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

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.

Discovery, Structure-Activity Relationships, and In Vivo Activity of Dihydropyridone Agonists of the Bile Acid Receptor TGR5

A novel series of potent agonists of the bile acid receptor TGR5 bearing a dihydropyridone scaffold was developed from a high-throughput screen. Starting from a micromolar hit compound, we implemented an extensive structure-activity-relationship (SAR) study with the synthesis and biological evaluation of 83 analogues. The project culminated with the identification of the potent nanomolar TGR5 agonist 77A. We report the GLP-1 secretagogue effect of our lead compound ex vivo in mouse colonoids and in vivo. In addition, to identify specific features favorable for TGR5 activation, we generated and optimized a three-dimensional quantitative SAR model that contributed to our understanding of our activity profile and could guide further development of this dihydropyridone series.

Integrative analysis revealed the role of glucagon-like peptide-2 in improving experimental colitis in mice by inhibiting inflammatory pathways, regulating glucose metabolism, and modulating gut microbiota

Introduction

Ulcerative colitis (UC) is an inflammatory bowel disease characterized by recurrent and remitting inflammation of the mucosa of the colon and rectum, the incidence of which is on the rise. Glucagon-like peptide-2 (GLP-2) is a newly discovered neurotrophic factor, but its efficacy and mechanism of action in UC remain unclear. In this study, we investigated the protective effects and potential targets of GLP-2 on dextran sodium sulfate (DSS)-induced UC in mice through integrative analysis.

Methods

The effects of GLP-2 on UC were assessed by calculating the disease activity index, colonic mucosal damage index, and pathological histological scores. Enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry were used to detect the expression of GLP-2, nuclear factor kappa-B (NF-κB), interleukin-6 (IL-6), and signal transducer and activator of transcription-3 (STAT3). The 16SrRNA gene was used to detect changes in gut microbiota in mouse colonic tissues, and oral glucose tolerance test (OGTT) blood glucose levels were used to analyze the differences in flora.

Results

The results showed that GLP-2 could reduce the inflammation of UC mice, which may be achieved by inhibiting the potential targets of NF-κB, and Janus kinase (JAK)/STAT3 inflammatory pathways, regulating sugar metabolism, increasing dominant species, and improving microbial diversity.

Discussion

This study provides new insight into the potential of GLP-2 for achieving more ideal UC treatment goals in future.

GLP-1 Receptor Agonists in Obese Patients with Inflammatory Bowel Disease: from Molecular Mechanisms to Clinical Considerations and Practical Recommendations for Safe and Effective Use

PURPOSE OF REVIEW

To discuss current literature and provide practical recommendations for the safe and effective use of glucagon-like peptide 1 receptor agonists (GLP-1 RA) in people with inflammatory bowel disease (IBD) and type 2 diabetes (T2D) and/or obesity. The molecular mechanisms that justify the potential benefits of GLP-1 RA in IBD and the links between IBD, obesity, and cardiovascular disease are also discussed.

RECENT FINDINGS

Preliminary data suggest that GLP-1 RA can modulate crucial pathways in the pathogenesis of IBD, such as chronic inflammation circuits, intestinal tight junctions, and gut microbiome dysbiosis, setting the stage for human trials to investigate the role of these agents in the treatment of IBD among people with or without diabetes and obesity. However, gastrointestinal side effects related to GLP-1 RA need appropriate clinical management to mitigate risks and maximize the benefits of therapy in people with IBD. GLP-1 RA originally emerged as drugs for the treatment of hyperglycemia and are currently licensed for the management of T2D and/or overweight/obesity. However, their wealth of pleiotropic actions soon raised expectations that they might confer benefits on non-metabolic disorders. Future studies are expected to clarify whether GLP-1 RA deserve an adjunct place in the arsenal of drugs against IBD.

Glepaglutide, a novel glucagon-like peptide-2 agonist, has anti-inflammatory and mucosal regenerative effects in an experimental model of inflammatory bowel disease in rats

BACKGROUND

Glucagon-like peptide-2 (GLP-2) enhances intestinal repair and attenuates inflammation in preclinical inflammatory bowel disease (IBD) models, making GLP-2 analogues attractive candidates for IBD therapy. Glepaglutide is a long-acting GLP-2 receptor agonist in clinical development for treatment of short bowel syndrome. Here, we investigated if glepaglutide is therapeutically beneficial in rats with small intestinal inflammation.

METHODS

Small intestinal inflammation was induced with indomethacin in naive Wistar rats, followed by glepaglutide administration at different disease stages. Glepaglutide was administered in co-treatment and post-treatment regimens. Small intestinal length and concentrations of inflammatory markers α-1-acid glycoprotein and myeloperoxidase were used to assess anti-inflammatory effects. Small intestinal mass was evaluated to determine intestinotrophic effects.

RESULTS

Glepaglutide co- and post-treatment significantly reduced severity of small intestinal inflammation, evidenced by reversed small intestinal shortening and decreased α-1-acid glycoprotein and/or myeloperoxidase concentration(s). Co- and post-treatment with glepaglutide also significantly increased small intestinal mass, indicating intestinal regenerative effects. Similar effects were observed in naive rats after glepaglutide treatment.

CONCLUSION

Glepaglutide has anti-inflammatory and intestinotrophic effects without the need for pre-treatment in a rat model of small intestinal inflammation. Thus, glepaglutide is of potential clinical interest for patients with IBD.

Biodegradable Polymeric Nanoparticles Loaded with Flavonoids: A Promising Therapy for Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a group of disorders that cause chronic non-specific inflammation in the gastrointestinal (GI) tract, primarily affecting the ileum and colon. The incidence of IBD has risen sharply in recent years. Despite continuous research efforts over the past decades, the aetiology of IBD is still not fully understood and only a limited number of drugs are available for its treatment. Flavonoids, a ubiquitous class of natural chemicals found in plants, have been widely used in the prevention and treatment of IBD. However, their therapeutic efficacy is unsatisfactory due to poor solubility, instability, rapid metabolism, and rapid systemic elimination. With the development of nanomedicine, nanocarriers can efficiently encapsulate various flavonoids and subsequently form nanoparticles (NPs), which greatly improves the stability and bioavailability of flavonoids. Recently, progress has also been made in the methodology of biodegradable polymers that can be used to fabricate NPs. As a result, NPs can significantly enhance the preventive or therapeutic effects of flavonoids on IBD. In this review, we aim to evaluate the therapeutic effect of flavonoid NPs on IBD. Furthermore, we discuss possible challenges and future perspectives.

Divergent roles for the gut intraepithelial lymphocyte GLP-1R in control of metabolism, microbiota, and T cell-induced inflammation

Gut intraepithelial lymphocytes (IELs) are thought to calibrate glucagon-like peptide 1 (GLP-1) bioavailability, thereby regulating systemic glucose and lipid metabolism. Here, we show that the gut IEL GLP-1 receptor (GLP-1R) is not required for enteroendocrine L cell GLP-1 secretion and glucose homeostasis nor for the metabolic benefits of GLP-1R agonists (GLP-1RAs). Instead, the gut IEL GLP-1R is essential for the full effects of GLP-1RAs on gut microbiota. Moreover, independent of glucose control or weight loss, the anti-inflammatory actions of GLP-1RAs require the gut IEL GLP-1R to selectively restrain local and systemic T cell-induced, but not lipopolysaccharide-induced, inflammation. Such effects are mediated by the suppression of gut IEL effector functions linked to the dampening of proximal T cell receptor signaling in a protein-kinase-A-dependent manner. These data reposition key roles of the L cell-gut IEL GLP-1R axis, revealing mechanisms linking GLP-1R activation in gut IELs to modulation of microbiota composition and control of intestinal and systemic inflammation.

Crosstalk between incretin hormones, Th17 and Treg cells in inflammatory diseases

Intestinal epithelial cells constantly crosstalk with the gut microbiota and immune cells of the gut lamina propria. Enteroendocrine cells, secrete hormones, such as incretin hormones, which participate in host physiological events, such as stimulating insulin secretion, satiety, and glucose homeostasis. Interestingly, evidence suggests that the incretin pathway may influence immune cell activation. Consequently, drugs targeting the incretin hormone signaling pathway may ameliorate inflammatory diseases such as inflammatory bowel diseases, cancer, and autoimmune diseases. In this review, we discuss how these hormones may modulate two subsets of CD4 + T cells, the regulatory T cells (Treg)/Th17 axis important for gut homeostasis: thus, preventing the development and progression of inflammatory diseases. We also summarize the main experimental and clinical findings using drugs targeting the glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide (GLP-1) signaling pathways and their great impact on conditions in which the Treg/Th17 axis is disturbed such as inflammatory diseases and cancer. Understanding the role of incretin stimulation in immune cell activation and function, might contribute to new therapeutic designs for the treatment of inflammatory diseases, autoimmunity, and tumors.

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.

A GLP-1/GLP-2 receptor dual agonist to treat NASH: Targeting the gut-liver axis and microbiome

BACKGROUND AND AIMS

Currently there is no Food and Drug Administration-approved drug to treat NAFLD and NASH, the rates of which are increasing worldwide. Although NAFLD/NASH are highly complex and heterogeneous conditions, most pharmacotherapy pipelines focus on a single mechanistic target. Considering the importance of the gut-liver axis in their pathogenesis, we investigated the therapeutic effect of a long-acting dual agonist of glucagon-like peptide (GLP)-1 and GLP-2 receptors in mice with NAFLD/NASH.

APPROACH AND RESULTS

C57BL/6J mice were fed a choline-deficient high-fat diet/high fructose and sucrose solution. After 16 weeks, mice were randomly allocated to receive vehicle, GLP1-Fc, GLP2-Fc, or GLP1/2-Fc fusion (GLP1/2-Fc) subcutaneously every 2 days for 4 weeks. Body weight was monitored, insulin/glucose tolerance tests were performed, feces were collected, and microbiome profiles were analyzed. Immobilized cell systems were used to evaluate direct peptide effect. Immunohistochemistry, quantitative PCR, immunoblot analysis, tunnel assay, and biochemical assays were performed to assess drug effects on inflammation, hepatic fibrosis, cell death, and intestinal structures. The mice had well-developed NASH phenotypes. GLP1/2-Fc reduced body weight, glucose levels, hepatic triglyceride levels, and cellular apoptosis. It improved liver fibrosis, insulin sensitivity, and intestinal tight junctions, and increased microvillus height, crypt depth, and goblet cells of intestine compared with a vehicle group. Similar effects of GLP1/2-Fc were found in in vitro cell systems. GLP1/2-Fc also changed microbiome profiles. We applied fecal microbiota transplantation (FMT) gain further insight into the mechanism of GLP1/2-Fc-mediated protection. We confirmed that FMT exerted an additive effect on GLP1-Fc group, including the body weight change, liver weight, hepatic fat accumulation, inflammation, and hepatic fibrosis.

CONCLUSIONS

A long-acting dual agonist of GLP-1 and GLP-2 receptors is a promising therapeutic strategy to treat NAFLD/NASH.

The enteroinsular axis during hospitalization in newborn foals

The enteroinsular axis (EIA) is an energy regulatory system that modulates insulin secretion through the release of enteroendocrine factors (incretins). Despite the importance of energy homeostasis in the equine neonate, information on the EIA in hospitalized foals is lacking. The goals of this study were to measure serum insulin and plasma incretin (glucose-dependent insulinotropic polypeptide [GIP], glucagon-like peptide-1 [GLP-1] and glucagon-like peptide-2 [GLP-2]) concentrations, to determine the insulin and incretin association, as well as their link to disease severity and outcome in hospitalized foals. A total of 102 newborn foals ≤72 h old were classified into hospitalized (n = 88) and healthy groups (n = 14). Hospitalized foals included septic (n = 55) and sick non-septic (SNS; n = 33) foals based on sepsis scores. Blood samples were collected over 72 h to measure serum insulin and plasma GIP, GLP-1 and GLP-2 concentrations using immunoassays. Data were analyzed by nonparametric methods and univariate logistic regression. At admission, serum glucose and insulin and plasma GIP were significantly lower in hospitalized and septic compared to healthy foals (P < 0.01), while plasma GLP-1 and GLP-2 concentrations were higher in hospitalized and septic foals than healthy and SNS foals, and decreased over time in septic foals (P < 0.05). As a percent of admission values, GLP-1 and GLP-2 concentrations dropped faster in healthy compared to hospitalized foals. Serum insulin concentrations were lower in hospitalized and septic non-survivors than survivors at admission (P < 0.01). Hospitalized foals with serum insulin < 5.8 µIU/mL, plasma GLP-1 >68.5 pM, and plasma GLP-2 >9 ng/mL within 24 h of admission were more likely to die (OR = 4.2; 95% CI = 1.1-16.1; OR = 13.5, 95% CI = 1.4-123.7; OR = 12.5, 95% CI = 1.6-97.6, respectively; P < 0.05). Low GIP together with increased GLP-1 and GLP-2 concentrations indicates that different mechanisms may be contributing to reduced insulin secretion in critically ill foals, including impaired intestinal production (GIP, proximal intestine) and pancreatic endocrine resistance to enhanced incretin secretion (GLP-1, GLP-2; distal intestine). These imbalances could contribute to energy dysregulation in the critically ill equine neonate.

A Novel Pathway of Flavonoids Protecting against Inflammatory Bowel Disease: Modulating Enteroendocrine System

Inflammatory bowel disease (IBD) is a comprehensive term for chronic or relapsing inflammatory diseases occurring in the intestinal tract, generally including Crohn's disease (CD) and ulcerative colitis (UC). Presently, the pathogenesis of IBD is unknown, yet multiple factors have been reported to be related with the development of IBD. Flavonoids are phytochemicals with biological activity, which are ubiquitously distributed in edible plants, such as fruits and vegetables. Recent studies have demonstrated impressively that flavonoids have anti-IBD effects through multiple mechanisms. These include anti-inflammatory and antioxidant actions; the preservation of the epithelial barrier integrity, the intestinal immunomodulatory property, and the shaping microbiota composition and function. In addition, a few studies have shown the impact of flavonoids on enterohormones release; nonetheless, there is hardly any work showing the link between flavonoids, enterohormones release and IBD. So far, the interaction between flavonoids, enterohormones and IBD is elucidated for the first time in this review. Furthermore, the inference can be drawn that flavonoids may protect against IBD through modulating enterohormones, such as glucagon-like peptide 1 (GLP-1), GLP-2, dipeptidyl peptidase-4 inhibitors (DPP-4 inhibitors), ghrelin and cholecystokinin (CCK). In conclusion, this manuscript explores a possible mechanism of flavonoids protecting against IBD.

Oral Delivery of Biologics in Inflammatory Bowel Disease Treatment

Inflammatory bowel disease (IBD) has been posed as a great worldwide health threat. Having an onset during early adulthood, IBD is a chronic inflammatory disease characterized by remission and relapse. Due to its enigmatic etiology, no cure has been developed at the moment. Conventionally, steroids, 5-aminosalicylic acid, and immunosuppressants have been applied clinically to relieve patients’ syndrome which, unfavorably, causes severe adverse drug reactions including diarrhea, anemia, and glaucoma. Insufficient therapeutic effects also loom, and surgical resection is mandatory in half of the patients within 10 years after diagnosis. Biologics demonstrated unique and differentiative therapeutic mechanism which can alleviate the inflammation more effectively. However, their application in IBD has been hindered considering their stability and toxicity. Scientists have brought up with the concept of nanomedicine to achieve the targeted drug delivery of biologics for IBD. Here, we provide an overview of biologics for IBD treatment and we review existing formulation strategies for different biological categories including antibodies, gene therapy, and peptides. This review highlights the current trends in oral delivery of biologics with an emphasis on the important role of nanomedicine in the development of reliable methods for biologic delivery in IBD treatment.

GLP-2 Is Locally Produced From Human Islets and Balances Inflammation Through an Inter-Islet-Immune Cell Crosstalk

Glucagon-like peptide-1 (GLP-1) shows robust protective effects on β-cell survival and function and GLP-1 based therapies are successfully applied for type-2 diabetes (T2D) and obesity. Another cleavage product of pro-glucagon, Glucagon-like peptide-2 (GLP-2; both GLP-1 and GLP-2 are inactivated by DPP-4) has received little attention in its action inside pancreatic islets. In this study, we investigated GLP-2 production, GLP-2 receptor (GLP-2R) expression and the effect of GLP-2R activation in human islets. Isolated human islets from non-diabetic donors were exposed to diabetogenic conditions: high glucose, palmitate, cytokine mix (IL-1β/IFN-γ) or Lipopolysaccharide (LPS) in the presence or absence of the DPP4-inhibitor linagliptin, the TLR4 inhibitor TAK-242, the GLP-2R agonist teduglutide and/or its antagonist GLP-2(3-33). Human islets under control conditions secreted active GLP-2 (full-length, non-cleaved by DPP4) into the culture media, which was increased by combined high glucose/palmitate, the cytokine mix and LPS and highly potentiated by linagliptin. Low but reproducible GLP-2R mRNA expression was found in all analyzed human islet isolations from 10 donors, which was reduced by pro-inflammatory stimuli: the cytokine mix and LPS. GLP-2R activation by teduglutide neither affected acute or glucose stimulated insulin secretion nor insulin content. Also, teduglutide had no effect on high glucose/palmitate- or LPS-induced dysfunction in cultured human islets but dampened LPS-induced macrophage-dependent IL1B and IL10 expression, while its antagonist GLP-2(3-33) abolished such reduction. In contrast, the expression of islet macrophage-independent cytokines IL6, IL8 and TNF was not affected by teduglutide. Medium conditioned by teduglutide-exposed human islets attenuated M1-like polarization of human monocyte-derived macrophages, evidenced by a lower mRNA expression of pro-inflammatory cytokines, compared to vehicle treated islets, and a reduced production of itaconate and succinate, marker metabolites of pro-inflammatory macrophages. Our results reveal intra-islet production of GLP-2 and GLP-2R expression in human islets. Despite no impact on β-cell function, local GLP-2R activation reduced islet inflammation which might be mediated by a crosstalk between endocrine cells and macrophages.

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 has a positive impact on osteoporosis in ovariectomized rats

AIMS

In this study, we evaluate the effects of glucagon-like peptide 2 (GLP-2) on bone microarchitecture, bone turnover markers (BTMs) and inflammation markers in ovariectomized (OVX) rats.

MATERIAL AND METHODS

In total, 31 Sprague-Dawley rats were divided into the following three groups: sham (control sham-operated with vehicle, n = 7), OV (OVX with vehicle, n = 12), and GLP-2 (OVX with GLP-2, n = 12). Intervention began at the 12th week after surgery and lasted for 4 weeks. The dosage of the GLP-2 was 160 μg/kg/d through subcutaneous injections, and normal saline was used as the vehicle agent. After 4 weeks of treatment, serum BTM and inflammation marker levels were measured by ELISA, and femora samples were analyzed by qRT-PCR, micro-CT, histology and histomorphometry.

KEY FINDINGS

After 4 weeks of treatment, serum TRAcP-5b and RANKL levels as well as the CTX-1/P1NP ratio in the GLP-2 group decreased, and ALP activity, P1NP level, and OPG/RANKL ratio increased significantly; qRT-PCR analysis showed that mRNA levels of RANKL decreased, and Runx2, ALP, and Col-1 levels as well as the OPG/RANKL ratio increased significantly in the GLP-2 group compared with the OV group. In bone histology analysis, GLP-2 significantly decreased the AV/MV, Oc.N and Oc.S but increased the Ob.N, BFR and MAR. Analysis with μ-CT showed that the BMD, BV/TV, Tb.N and Conn.D increased significantly in the GLP-2 group compared with the OV group. The levels of serum inflammation markers TNF-α, IL-1β and IL-6 decreased, and TGF-β levels increased in the GLP-2 group compared with the OV group.

SIGNIFICANCE

GLP-2 may have a positive impact on osteoporosis by promoting bone formation, inhibiting bone resorption and decreasing circulatory inflammation in ovariectomized rats.

Purified PEGylated human glucagon-like peptide-2 reduces the severity of irradiation-induced acute radiation enteritis in rats

Radiation-induced acute intestinal injury after abdominal and pelvic irradiation is a common and serious problem in the clinical setting. Glucagon-like peptide-2 (GLP-2), a 33-amino acid peptide, exerts diverse effects related to the regulation of gastrointestinal growth and function. However, GLP-2 is relatively unstable in vivo. The aim of the present study was to improve GLP-2 stability in vivo and to evaluate its therapeutic effect on acute radiation enteritis. We generated long-lasting intestinal protection peptides by conjugating human GLP-2 (hGLP-2) peptides to polyethyleneglycol (PEG) to produce mPEGylation hGLP-2 (Mono-PEG-hGLP-2) through an enzymatic site-specific transglutamination reaction. Mono-PEG-hGLP-2 synthesized under optimal reaction conditions and separated by one-step ion-exchange chromatography was found to be resistant to degradation in vitro. Pretreatment with Mono-PEG-hGLP-2 reduced the severity of radiation-induced intestinal injury, oxidative stress, and the expression of NF-κB in rats with irradiation-induced acute radiation enteritis. The enhanced biological potency of Mono-PEG-hGLP-2 highlights its potential as a therapeutic agent for intestinal diseases.

Glucagon-like peptide-2 reduces the obesity-associated inflammation in the brain

Growing evidence suggests a link between obesity and neurodegeneration. The purpose of the present study was to explore the neuroprotective potential of glucagon-like peptide-2 (GLP-2) in the brain of high fat diet (HFD)-fed mice. Markers of inflammation and oxidative stress were analysed in the brains of obese mice chronically treated with [Gly²]-GLP-2 (teduglutide), the stable analogue of the GLP-2, and they were compared to age-matched untreated obese and lean animals. Neurodegeneration was examined by TUNEL assay. HFD feeding increased the expression of pro-inflammatory mediators (NF-kB, IL-8, TNF-α, IL-1β and IL-6), glial fibrillary acidic protein (GFAP), index of gliosis and neurodegeneration, stress marker proteins (p-ERK, Hsp60 and i-NOS), amyloid-β precursor protein (APP). [Gly²]-GLP-2 treatment significantly attenuated the HFD-induced increased expression of the various markers, as well as the higher levels of reactive oxygen species found in brains of untreated-HFD mice. Immunofluorescence confirmed that the increase of GFAP or APP in the brain cortex of HFD mice were less prominent in the [Gly²]-GLP-2 treated group. TUNEL-positive cell number in brain sections of [Gly²]-GLP-2-treated HFD-fed mice was significantly lesser in comparison with untreated-HFD animals and similar to STD fed mice. In conclusion, the results of the present study suggest that GLP-2 stable analogue improves the obesity-associated neuroinflammation and the central stress conditions, it reduces the neuronal apoptotic death, providing evidence for a neuroprotective role of the peptide.

Starch Tolerance and the Short Bowel

Short bowel syndrome with intestinal failure is a rare disease with a massive impairment in quality of life, requiring a multidisciplinary team approach to medical, surgical, and nutritional therapy. Current pharmacological and surgical therapeutic options are limited; an important cornerstone is enteral and parenteral nutrition. The changed physiology of carbohydrate digestion plays a major role in the adaptation process and can be a target for specific enteral nutrition interventions. An important prognostic factor is the preservation of at least portions of the colon in continuity with small bowel. This strategy has to include an evaluation of the anatomical situation and small bowel absorptive capacity, adaptation processes, and luminal microbiota including its fermentative properties. Starch is probably the most important complex carbohydrate in short bowel syndrome nutrition, because it is absorbed or fermented almost completely. Benefits of supplementation with complex carbohydrates include improved adaptive processes, positive trophic effects on the mucosa and its hormonal response, longer transit time, and possibly a faster time to wean from parenteral nutrition, but supplementation advice needs to weigh carefully the risks and benefits, especially considering bacterial overgrowth, osmotic load, and D-lactate acidosis.

Factors Associated With Response to Teduglutide in Patients With Short-Bowel Syndrome and Intestinal Failure

BACKGROUND & AIMS

Clinical studies showed teduglutide to increase urine production and reduce need for parenteral support volume in patients with short bowel syndrome (SBS) with intestinal failure, increasing intestinal wet weight absorption and reducing diarrhea. However, the effects of teduglutide on parenteral support vary among patients. We performed a post hoc analysis of a phase III placebo-controlled study to identify characteristics of patients in whom teduglutide has the largest effects on parenteral support volume response.

METHODS

We collected data from 85 patients with SBS with intestinal failure, according to the European Society for Clinical Nutrition and Metabolism classification system, who received teduglutide or placebo between November 25, 2008, and January 4, 2011, at 27 sites in 10 countries. Changes in parenteral support volume were evaluated according to baseline parenteral support volume, bowel anatomy (group 1, jejunostomy/ileostomy; group 2, ≥50% colon-in-continuity without stoma; and group 3, other colon anatomies), and disease features (with inflammatory bowel disease, mesenteric vascular diseases, or other conditions). Correlation analyses were conducted using simple linear regression models, with unadjusted r² values reported. Two-sided t tests were used for comparisons between treatment groups.

RESULTS

We correlated parenteral support volume reduction with teduglutide treatment and baseline parenteral support volume (y = -0.3870x + 90.0279, r² = 0.61; P < .0001). The effects of teduglutide on absolute parenteral support volume were significantly greater in group 1 patients (reduction of 919 ± 644 mL/d), not only compared with patients given placebo (reduction of 340 ± 436 mL/d; P = .0112) but also compared with teduglutide-treated patients in group 2 (reduction of 355 ± 306 mL/d; P = .0066). Teduglutide had an intermediate effect on patients in group 3. A minority of patients with SBS and inflammatory bowel diseases had colon-in-continuity (10.5% [n = 2/19]), whereas most patients with SBS and vascular or other diseases had colon-in-continuity (84.4% [n = 27/32] and 67.6% [n = 23/34], respectively).

CONCLUSIONS

In a post hoc analysis of data from a phase III study of the effects of teduglutide on patients with SBS, we associated reduced parenteral support volume with baseline parenteral support volume, bowel anatomy, and SBS features. These findings may inform initial parenteral support volume adjustments and management of these severely disabled patients. ClinicalTrials.gov no: NCT00798967; ClinicalTrialsRegister.eu no: 2008-006193-15.

Enteroendocrine cells-sensory sentinels of the intestinal environment and orchestrators of mucosal immunity

The intestinal epithelium must balance efficient absorption of nutrients with partitioning commensals and pathogens from the bodies' largest immune system. If this crucial barrier fails, inappropriate immune responses can result in inflammatory bowel disease or chronic infection. Enteroendocrine cells represent 1% of this epithelium and have classically been studied for their detection of nutrients and release of peptide hormones to mediate digestion. Intriguingly, enteroendocrine cells are the key sensors of microbial metabolites, can release cytokines in response to pathogen associated molecules and peptide hormone receptors are expressed on numerous intestinal immune cells; thus enteroendocrine cells are uniquely equipped to be crucial and novel orchestrators of intestinal inflammation. In this review, we introduce enteroendocrine chemosensory roles, summarize studies correlating enteroendocrine perturbations with intestinal inflammation and describe the mechanistic interactions by which enteroendocrine and mucosal immune cells interact during disease; highlighting this immunoendocrine axis as a key aspect of innate immunity.

Role of Incretin Axis in Inflammatory Bowel Disease

The inflammatory bowel diseases (IBDs), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic inflammatory conditions of the gastrointestinal tract and involve a complicated reciprocity of environmental, genetic, and immunologic factors. Despite substantial advances in the foundational understanding of the immunological pathogenesis of IBD, the detailed mechanism of the pathological progression in IBD remains unknown. In addition to Th1/Th2 cells, whose role in IBD has been previously well defined, recent evidence indicates that Th17 cells and Tregs also play a crucial role in the development of IBD. Diets which contain excess sugars, salt, and fat may also be important actors in the pathogenesis of IBD, which may be the cause of high IBD incidence in western developed and industrialized countries. Up until now, the reason for the variance in prevalence of IBD between developed and developing countries has been unknown. This is partly due to the increasing popularity of western diets in developing countries, which makes the data harder to interpret. The enterocrinins glucagon-like peptides (GLPs), including GLP-1 and GLP-2, exhibit notable benefits on lipid metabolism, atherosclerosis formation, plasma glucose levels, and maintenance of gastric mucosa integrity. In addition to the regulation of nutrient metabolism, the emerging role of GLPs and their degrading enzyme dipeptidyl peptidase-4 (DPP-4) in gastrointestinal diseases has gained increasing attention. Therefore, here we review the function of the DPP-4/GLP axis in IBD.

Intestinal inflammatory and redox responses to the perioperative administration of teduglutide in rats

Purpose:

To investigate the inflammatory and redox responses to teduglutide on an animal model of laparotomy and intestinal anastomosis.

Methods:

Wistar rats (n=62) were allocated into four groups: "Ileal Resection and Anastomosis" vs. "Laparotomy", each one split into "Postoperative Teduglutide Administration" vs. "No Treatment"; and euthanized at the third or the seventh day. Ileal and blood samples were recovered at the baseline and at the euthanasia. Flow cytometry was used to study the inflammatory response (IL-1α, MCP-1, TNF-α, IFN-γ and IL-4 levels), oxidative stress (cytosolic peroxides, mitochondrial reactive species, intracellular glutathione and mitochondrial membrane potential) and cellular viability and death (annexin V/propidium iodide double staining).

Results:

Postoperative teduglutide treatment was associated with higher cellular viability index and lower early apoptosis ratio at the seventh day; higher cytosolic peroxides level at the third day and mitochondrial overgeneration of reactive species at the seventh day; higher tissue concentration of IL-4 and lower local pro-to-anti-inflammatory cytokines ratio at the seventh day.

Conclusion:

Those findings suggest an intestinal pro-oxidative and anti-inflammatory influence of teduglutide on the peri-operative context with a potential interference in the intestinal anastomotic healing.

Therapeutic effects of different doses of polyethylene glycosylated porcine glucagon-like peptide-2 on ulcerative colitis in male rats

BACKGROUND

Polyethylene glycosylated (PEGylated) porcine glucagon-like peptide-2 (pGLP-2) considerably increases half-life and stability compared with the native pGLP-2, but the effective dose for intestinal damage is still unclear. This study aims to evaluate the available dose of polyethylene glycosylated porcine glucagon-like peptide-2 (PEG-pGLP-2), a modified, long-acting form of pGLP-2 in an experimental rat model of ulcerative colitis.

METHODS

Thirty-five male rats were randomly assigned into five groups: control, dextran sodium sulphate (DSS), DSS + PEG-pGLP-2(L), DSS + PEG-pGLP-2(M) and DSS + PEG-pGLP-2(H). Rats in control group received only water; other rats were fed with 5% (w/v) DSS and intraperitoneally administered with 12.5, 25 and 100 nmol/kg PEG-pGLP-2 daily for 6 days.

RESULTS

Compared with the control treatment, DSS treatment significantly (p < 0.05) decreased body weight change, colonic length, duodenal villus height and expression of zonula occludens-1, whereas significantly (p < 0.05) increased colonic damage score and expression of claudin-1, interleukin (IL)-1, IL-7, IL-10, interferon-γ and tumour necrosis factor (TNF)-α in colon. However, the three doses of PEG-pGLP-2 all reduced these effects; these treatments significantly (p < 0.05) increased body weight change and duodenal villus height, whereas significantly (p < 0.05) decreased colonic damage score and expression of IL-1, IL-7 and TNF-α in colon. Specifically, low-dose (12.5 nmol/kg/d) PEG-pGLP-2 was effective.

CONCLUSIONS

These results indicated that PEG-pGLP-2 is a novel and potentially effective therapy for intestinal healing in a relatively low dose.

GLP-2 Attenuates LPS-Induced Inflammation in BV-2 Cells by Inhibiting ERK1/2, JNK1/2 and NF-κB Signaling Pathways

The pathogenesis of Parkinson’s disease (PD) often involves the over-activation of microglia. Over-activated microglia could produce several inflammatory mediators, which trigger excessive inflammation and ultimately cause dopaminergic neuron damage. Anti-inflammatory effects of glucagon-like peptide-2 (GLP-2) in the periphery have been shown. Nonetheless, it has not been illustrated in the brain. Thus, in this study, we aimed to understand the role of GLP-2 in microglia activation and to elucidate the underlying mechanisms. BV-2 cells were pretreated with GLP-2 and then stimulated by lipopolysaccharide (LPS). Cells were assessed for the responses of pro-inflammatory enzymes (iNOS and COX-2) and pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α); the related signaling pathways were evaluated by Western blotting. The rescue effect of GLP-2 on microglia-mediated neurotoxicity was also examined. The results showed that GLP-2 significantly reduced LPS-induced production of inducible nitric oxide synthase (iNOS), cyclooxygenase-s (COX-2), IL-1β, IL-6 and TNF-α. Blocking of Gα_s by NF449 resulted in a loss of this anti-inflammatory effect in BV-2 cells. Analyses in signaling pathways demonstrated that GLP-2 reduced LPS-induced phosphorylation of ERK1/2, JNK1/2 and p65, while no effect was observed on p38 phosphorylation. In addition, GLP-2 could suppress microglia-mediated neurotoxicity. All results imply that GLP-2 inhibits LPS-induced microglia activation by collectively regulating ERK1/2, JNK1/2 and p65.

GLP-2 Prevents Intestinal Mucosal Atrophy and Improves Tissue Antioxidant Capacity in a Mouse Model of Total Parenteral Nutrition

We investigated the effects of exogenous glucagon-like peptide-2 (GLP-2) on mucosal atrophy and intestinal antioxidant capacity in a mouse model of total parenteral nutrition (TPN). Male mice (6–8 weeks old) were divided into three groups (n = 8 for each group): a control group fed a standard laboratory chow diet, and experimental TPN (received standard TPN solution) and TPN + GLP-2 groups (received TPN supplemented with 60 µg/day of GLP-2 for 5 days). Mice in the TPN group had lower body weight and reduced intestinal length, villus height, and crypt depth compared to the control group (all p < 0.05). GLP-2 supplementation increased all parameters compared to TPN only (all p < 0.05). Intestinal total superoxide dismutase activity and reduced-glutathione level in the TPN + GLP-2 group were also higher relative to the TPN group (all p < 0.05). GLP-2 administration significantly upregulated proliferating cell nuclear antigen expression and increased glucose-regulated protein (GRP78) abundance. Compared with the control and TPN + GLP-2 groups, intestinal cleaved caspase-3 was increased in the TPN group (all p < 0.05). This study shows GLP-2 reduces TPN-associated intestinal atrophy and improves tissue antioxidant capacity. This effect may be dependent on enhanced epithelial cell proliferation, reduced apoptosis, and upregulated GRP78 expression.

Bugs, genes, fatty acids, and serotonin: Unraveling inflammatory bowel disease?

The annual incidence of the inflammatory bowel diseases (IBDs) ulcerative colitis and Crohn's disease has increased at an alarming rate. Although the specific pathophysiology underlying IBD continues to be elusive, it is hypothesized that IBD results from an aberrant and persistent immune response directed against microbes or their products in the gut, facilitated by the genetic susceptibility of the host and intrinsic alterations in mucosal barrier function. In this review, we will describe advances in the understanding of how the interaction of host genetics and the intestinal microbiome contribute to the pathogenesis of IBD, with a focus on bacterial metabolites such as short chain fatty acids (SCFAs) as possible key signaling molecules.  In particular, we will describe alterations of the intestinal microbiota in IBD, focusing on how genetic loci affect the gut microbial phylogenetic distribution and the production of their major microbial metabolic product, SCFAs. We then describe how enteroendocrine cells and myenteric nerves express SCFA receptors that integrate networks such as the cholinergic and serotonergic neural systems and the glucagon-like peptide hormonal pathway, to modulate gut inflammation, permeability, and growth as part of an integrated model of IBD pathogenesis.  Through this integrative approach, we hope that novel hypotheses will emerge that will be tested in reductionist, hypothesis-driven studies in order to examine the interrelationship of these systems in the hope of better understanding IBD pathogenesis and to inform novel therapies.

Teduglutide-Stimulated Intestinal Adaptation Is Complemented and Synergistically Enhanced by Partial Enteral Nutrition in a Neonatal Piglet Model of Short Bowel Syndrome

BACKGROUND

Teduglutide, a glucagon-like peptide-2 (GLP-2) analogue, is available for long-term use by parenteral nutrition (PN)-dependent adults to promote intestinal adaptation but is not approved for use in pediatric patients. The objective of this study was to assess teduglutide-stimulated induced intestinal adaptation, potential synergies with partial enteral nutrition (PEN), and distinct temporal markers of adaptation in a neonatal piglet model of short bowel syndrome (SBS).

MATERIALS AND METHODS

Neonatal piglets (48 hours old; n = 72) underwent an 80% jejunoileal resection and were randomized to 1 of 4 treatment groups, in a 2 × 2 factorial design, with PN or PEN (80% standard PN/20% standard enteral nutrition) and teduglutide (0.1 mg/kg/d) or control. Piglets received nutrient infusions for 4 hours, 48 hours, or 7 days.

RESULTS

Teduglutide improved ( P < .05) mucosal surface area (villus height: duodenum, jejunum, ileum; crypt depth: ileum, colon; proliferation: duodenum, jejunum, ileum; colon; apoptosis: jejunum, ileum, colon) and acute nutrient processing capacity (glucose: duodenum, jejunum, ileum; glutamine: duodenum, jejunum). These effects were complemented and synergistically enhanced by PEN in both site and timing of action. Structural adaptations preceded functional adaptations, but crypt depth remained a strong indicator of adaptation, regardless of time.

CONCLUSIONS

The combination of teduglutide and PEN enhances intestinal adaptation beyond that of either therapy alone.

Glucagon-like peptide-2 exhibits protective effect on hepatic ischemia-reperfusion injury in rats

Glucagon-like peptide-2 (GLP-2) has potent anti-inflammatory effects and protects against experimental ischemia/reperfusion (I/R) injury in pulmonary, intestinal, and myocardial tissue. However, its protective abilities against I/R injury in the liver are unknown. We investigated the potential role of GLP-2 pretreatment on hepatic I/R injury in rats. A total of 24 rats were randomly divided into three groups (n = 8). The first group was the control group; the second group was the vehicle-treated hepatic ischemia/reperfusion (HIR, vehicle saline-treated) group; and the third group was the GLP-2 pretreated I/R (GLP2-IR) group. Each rat in the third group was intraperitoneally administered 5 µg GLP-2 for 5 d before the procedure. A portal triad was created to induce ischemia with a vascular atraumatic clamp. After 40 min, the clamp was released to initiate hepatic reperfusion for 6 h. Blood samples and tissue specimens from the liver were obtained. Alanine aminotransferase, aspartate aminotransferase, and total bilirubin levels significantly increased in the salinetreated HIR group (P < 0.001), whereas GLP-2 pretreatment significantly decreased their levels (P < 0.01). Our data suggested that GLP-2 pretreatment may have a protective effect on liver I/R injury. However, dose-response studies are necessary to determine the most effective dose.

Bile acid mediated effects on gut integrity and performance of early-weaned piglets

Background

Early weaning (EW) results in a transient period of impaired integrity of the intestinal mucosa that may be associated with reduced plasma concentration of glucagon-like peptide-(GLP) 2. We have previously shown that intragastric infusion of chenodeoxycholic acid (CDC) increases circulating GLP-2 in early-weaned piglets. The aim of this study was to expand previous work to establish whether feeding piglets a cereal-based diet supplemented with CDC can improve gut integrity and animal performance immediately after EW. A cohort of 36 piglets weaned at 20 days of age, 6.2 ± 0.34 kg of body weight (BW) were randomly assigned (n = 18) to receive a standard prestarter diet or the same diet supplemented with 60 mg of CDC per kg of initial BW for ad libitum intake until day 14 postweaning. Thereafter, all pigs were fed the same untreated starter diet for 21 days until the end of the study on day 35. On days 1, 7 and 14 blood samples were collected from 6 pigs per treatment to measure plasma GLP-2. On day 15, 6 pigs per treatment were euthanized to obtain intestinal tissue samples for later histological and gene expression analyses.

Results

Supplementing the diet with CDC tended to increase plasma GLP-2 (P < 0.07; 39 %) and the weight of the large intestine (P < 0.10; 11 %), and increased ileal crypt depth (P < 0.04; 15 %) after 14 days of treatment exposure. Although feed intake and BW gain were not affected by treatments, feeding CDC induced the expression of the cytokines TNF-α (P < 0.02; 1.9 fold), IL-6 (P < 0.01; 2.4 fold), and IL-10 (P < 0.006; 2.2 fold) and the tight junctional protein ZON-1 (P < 0.02; 1.5 fold) in the distal small intestine.

Conclusions

This study showed that the oral administration of CDC to early-weaned pigs has the potential to improve the protection of the intestinal mucosa independently of relevant changes in gut growth.

Protective effect of glucagon-like peptide-2 in experimental corrosive esophagitis

Corrosive esophageal injuries are one of the life-threatening morbidities leading to esophageal stricture and perforation affecting all age groups but especially children due to accidental ingestions in this age group. Glucagon-like peptide-2 (GLP-2) is an intestinal polypeptide with potent anti-inflammatory effects. Its effects are studied in various studies but not in corrosive esophagitis. We aimed to investigate whether it has protective effect in experimental corrosive esophagitis, in the absence of existing studies into possible links. Twenty-four Wistar-albino rats, weighing 220-240 g, were randomized into three groups (n = 8 in each). First group is control, second one is sham operated, and the third one is treatment group. Median laparotomy was made in all groups. In sham and treatment groups, esophagus was loosened and suspended from 1 cm proximal to the esophageal junction. The esophagus segment between suspenders was exposed to 0.1 mL 5% NaOH for 10 seconds. In the treatment group, rats were given GLP-2 for 7 days intraperitoneally. After 7 days, all rats were sacrified and esophagi were totally removed. In the histopathologic examination, esophageal tissues were compared in terms of inflammation, muscularis mucosa injury, and collagen deposition of tunica muscularis. Histopathologic changes in the esophageal tissues of groups were compared. Histopathologic injury in the GLP-2 treated group was significantly less than sham group (P < 0.05). There was statistically significant healing in the GLP-2 treatment group. It is concluded that GLP-2 has a preventive effect on inflammation and collagen accumulation in an experimental corrosive esophagitis. In the light of the information that initial lesions in the early phase are predictors of complications, GLP-2 is a promising agent that has an anti-inflammatory effect in caustic injuries.

Gut hormones in the treatment of short-bowel syndrome and intestinal failure

PURPOSE OF REVIEW

The approval of teduglutide, a recombinant analog of human glucagon-like peptide (GLP) 2, by the US Food and Drug Administration (Gattex) and the European Medicines Agency (Revestive) has illustrated the potential of selected gut hormones as treatments in patients with short-bowel syndrome and intestinal failure. Gut hormones may improve the structural and functional intestinal adaptation following intestinal resection by decreasing a rapid gastric emptying and hypersecretion, by increasing the intestinal blood flow, and by promoting intestinal growth. This review summarizes the findings from phase 2 and 3 teduglutide studies, and pilot studies employing GLP-1 and agonists for this orphan condition.

RECENT FINDINGS

In a 3-week, phase 2, metabolic balance study, teduglutide increased the intestinal wet weight absorption by approximately 700 g/day and reduced fecal energy losses by approximately 0.8 MJ/day (∼200 Kcal/day). In two subsequent 24-week, phase 3 studies, teduglutide reduced the need for parenteral support in the same magnitude. Adverse events were mainly of gastrointestinal origin and consistent with the known mechanism of action of teduglutide. Pilot studies suggest that GLP-1 may be less potent. Synergistic effects may be seen by co-treatment with GLP-2.

SUMMARY

Gut hormones promote intestinal adaptation and absorption, decreasing fecal losses, thereby decreasing or even eliminating the need for parenteral support. This will aid the intestinal rehabilitation in these severely disabled short-bowel syndrome patients.

Glucagon-like peptide-2-induced memory improvement and anxiolytic effects in mice

We investigated the effectiveness of glucagon-like peptide-2 (GLP-2) on memory impairment in lipopolysaccharide (LPS)-treated mice, and anxiety-like behavior in adrenocorticotropic hormone (ACTH)-treated mice. In the Y-maze test, LPS (10 µg/mouse, i.c.v.) significantly decreased spontaneous alternation, which was prevented by pretreatment with GLP-2 (0.01-0.3 µg/mouse, i.c.v.). The GLP-2 treatment just before the Y-maze test also improved LPS-induced memory impairment. Continuous treatment with GLP-2 (3 µg/mouse, i.c.v.) had no effect on the open-field test in saline-treated or ACTH-treated mice. Chronic ACTH treatment did not cause anxiogenic effects in the elevated plus-maze test. GLP-2 showed weak anxiolytic-like effects in the elevated plus-maze test in ACTH-treated, but not saline-treated mice. Moreover, GLP-2 increased 5-HT, but not 5-HIAA and tryptophan hydroxylase 2 levels in the amygdala of ACTH-treated mice. Pharmacological depletion of 5-HT prevented the anxiolytic effects of GLP-2. These results suggest that GLP-2 protected and improved memory function in LPS-treated mice, and also had anxiolytic effects due to changes in the 5-HT system.

Exogenous glucagon-like peptide-2 improves outcomes of intestinal adaptation in a distal-intestinal resection neonatal piglet model of short bowel syndrome

BACKGROUND

Endogenous glucagon-like peptide-2 (GLP-2) levels and intestinal adaptation are reduced in distal-intestinal resection animal models of short bowel syndrome (SBS) that lack remnant ileum. We hypothesized that exogenous GLP-2 would improve intestinal adaptation in a distal-intestinal resection neonatal piglet model of SBS.

METHODS

In all, 35 piglets were randomized to 2 treatment and 3 surgical groups: control (sham), 75% mid-intestinal resection (JI), and 75% distal-intestinal resection (JC). Parenteral nutrition (PN) commenced on day 1 and was weaned as enteral nutrition (EN) advanced. IV GLP-2 (11 nmol/kg/d) or saline was initiated on day 2. Piglets were maintained for 14 d. Clinical, functional, morphological, and histological outcomes were obtained.

RESULTS

JC-GLP-2 piglets had fewer days on PN (10.0 ± 0.6 vs. 13.8 ± 0.2), more days on EN (4.0 ± 0.6 vs. 0.2 ± 0.2), a higher percentage of EN at termination (92 ± 5 vs. 52 ± 10%), fewer days of diarrhea (8.0 ± 0.7 vs. 12.3 ± 0.4), increased intestinal length (19 ± 4 vs. -5 ± 3%), and deeper jejunal crypts (248 ± 21 vs. 172 ± 12 μm), compared with saline piglets.

CONCLUSION

GLP-2 therapy improves clinical, morphological, and histological outcomes of intestinal adaptation in a distal-intestinal resection model of SBS. Since this anatomical subtype represents the majority of clinical cases of neonatal SBS, these results support a potential role for GLP-2 therapy in pediatric SBS.

Effects of PEGylated porcine glucagon-like peptide-2 therapy in weaning piglets challenged with lipopolysaccharide

This study aims to evaluate the therapeutic effect of polyethylene glycosylated porcine glucagon-like peptide-2 (pGLP-2), a long-acting form of pGLP-2, in lipopolysaccharide (LPS)-challenged piglets. Eighteen 21-day-old weaning piglets were randomly assigned into three groups: control (saline solution), LPS (100 μg/kg LPS), and PEG-pGLP-2 (10 nmol/kg PEG-pGLP-2+100 μg/kg LPS). All treatments were administered intraperitoneally. Compared with the control treatment, LPS treatment significantly decreased (P<0.05) the villus heights of the duodenum and jejunum, as well as the villus height/crypt depth ratio of the jejunum. However, PEG-pGLP-2 therapy reduced these effects (P>0.05). Specifically, PEG-pGLP-2 infusion significantly increased the villus height/crypt depth ratio of the duodenum (P<0.05) compared with LPS treatment. Compared with the control treatment, LPS treatment significantly increased (P<0.05) the mRNA expression levels of interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) in the jejunum. However, PEG-pGLP-2 therapy reduced these effects (P<0.05). Specifically, PEG-pGLP-2 infusion significantly decreased (P<0.05) the mRNA expression levels of interleukin (IL)-8 and TNF-α in the duodenum and jejunum, IL-10 in the duodenum, and IFN-γ in the jejunum compared with the LPS treatment. LPS treatment increased the caspase-3 activity of the ileum mucosal (P<0.05), and this effect was significantly reduced by PEG-pGLP-2 treatment. These results indicate that PEG-pGLP-2 infusion alleviates the severity of intestinal injury in weaning piglets by reducing the secretion of inflammatory cytokines and the caspase-3 activity, and increasing the villus height/crypt depth ratio.

Inflammation-induced functional connectivity of melanin-concentrating hormone and IL-10

Melanin-concentrating hormone (MCH) was identified in mammals as a hypothalamic neuropeptide regulating appetite and energy balance. However, similarly to most of the brain peptides, MCH is also produced in the gastrointestinal system and can act locally as an immunomodulator. We have previously reported high expression of MCH and its receptor MCHR1 in the affected mucosa of patients with inflammatory bowel disease. Furthermore, MCH deficiency in mice attenuated experimental colitis, pointing to MCH as a mediator of intestinal inflammation. In the present study, in order to gain further insights into the underlying mechanisms of such effects of MCH, we treated mice with established experimental colitis due to IL-10 deficiency with a MCHR1 antagonist (DABA-822). While treatment with the same drug was successful in attenuating TNBS-induced colitis in previous studies, it offered no benefit to the IL-10 knockout mouse model, suggesting that perhaps IL-10 is a downstream target of MCH. Indeed, in experiments focusing on monocytes, we found that treatment with MCH inhibited LPS-mediated IL-10 upregulation. Conversely, in the same cells, exogenous IL-10 prevented LPS-induced MCHR1 expression. Taken together, these findings indicate a functional cross-talk between MCH and IL-10 which prevents resolution of inflammation.

New approaches to the treatments of short bowel syndrome-associated intestinal failure

PURPOSE OF REVIEW

Teduglutide, a recombinant analog of human glucagon-like peptide 2, has recently been approved in the US and Europe (Gattex and Revestive, respectively) as the first targeted treatment of short bowel syndrome-associated intestinal failure (SBS-IF). Glucagon-like peptide 2 improves structural and functional intestinal adaptation following intestinal resection by decelerating a rapid gastric emptying, by decreasing gastric hypersecretion, by increasing intestinal blood flow and by promoting intestinal growth. This review summarizes the findings from phase 2 and 3 studies preceding the US Food and Drug Administration and the European Medicines Agency approval of subcutaneous teduglutide for this orphan condition.

RECENT FINDINGS

In a 3-week, phase 2, metabolic balance study, teduglutide increased intestinal wet weight absorption by approximately 700 g/day and reduced fecal energy losses by approximately 0.8 MJ/day (∼200 kcal/day). In two subsequent 24-week, phase 3 studies, teduglutide reduced the need for parenteral support in the same magnitude. Teduglutide had an acceptable tolerability profile, where adverse events generally were of gastrointestinal origin consistent with the known mechanism of action.

SUMMARY

Teduglutide will add incremental benefit to the limited medical treatment armamentarium in SBS patients by maximizing intestinal absorption, decreasing fecal losses, thereby decreasing or even eliminating the need for parenteral support. Future research should target and implement other key hormones with similar and possible additive or synergistic effects, thereby further promoting structural and functional adaptation and intestinal rehabilitation in these severely disabled SBS patients.

Purified PEGylated porcine glucagon-like peptide-2 reduces the severity of colonic injury in a murine model of experimental colitis

The rapid degradation of porcine glucagon-like peptide-2 (pGLP-2) by the enzyme dipeptidyl peptidase-IV (DPP-IV) is the main impediment in the development of pGLP-2 as a potential therapeutic agent for intestinal dysfunction and damage. In this study, one mono-modified Lys(30)-polyethylene glycol (PEG)-pGLP-2 was prepared using mPEG-succinimidyl propionate. To determine the optimized condition for PEGylation, the reactions were monitored by RP-HPLC and MALDI-TOF-MS. Stability was tested in purified DPP-IV in vitro. In vivo, the protective effects for colonic injury were measured in dextran sulfate sodium (DSS)-induced colitis in mice. The monoPEGylated products reached the maximum yield at 4:1 ratio of mPEG5k-SPA to pGLP-2. An effective method of successfully separating PEGylated pGLP-2 from mPEG-SPA5kD using CM Sepharose Fast Flow resin was established. The half-life of Lys(30)-PEG-pGLP-2 was 16-fold longer than that of pGLP-2 in DPP-IV. The DSS mice exhibited marked weight loss), which was significantly reduced by Lys(30)-PEG-pGLP-2 therapy. DSS treatment significantly increased colonic damage score, which was significantly reduced by administration of Lys(30)-PEG-pGLP-2 in DSS-mice. DSS-induced colitis clearly induced Myeloperoxidase activity in the colon, which was significantly reduced by treatments with 3% DSS-pGLP-2 or 3% DSS-PEG-pGLP-2. These results showed that site-specific Lys(30)-PEG-GLP-2 was resistant to degradation and reduced the severity of colonic injury in murine colitis. The enhanced biological potency of this product highlighted its potential as a therapeutic agent for intestinal diseases.

Physiology and pharmacology of the enteroendocrine hormone glucagon-like peptide-2

Glucagon-like peptide-2 (GLP-2) is a 33-amino-acid proglucagon-derived peptide secreted from enteroendocrine L cells. GLP-2 circulates at low basal levels in the fasting period, and plasma levels rise rapidly after food ingestion. Renal clearance and enzymatic inactivation control the elimination of bioactive GLP-2. GLP-2 increases mesenteric blood flow and activates proabsorptive pathways in the gut, facilitating nutrient absorption. GLP-2 also enhances gut barrier function and induces proliferative and cytoprotective pathways in the small bowel. The actions of GLP-2 are transduced via a single G protein-coupled receptor (GLP-2R), expressed predominantly within the gastrointestinal tract. Disruption of GLP-2R signaling increases susceptibility to gut injury and impairs the adaptive mucosal response to refeeding. Sustained augmentation of GLP-2R signaling reduces the requirement for parenteral nutrition in human subjects with short-bowel syndrome. Hence GLP-2 integrates nutrient-derived signals to optimize mucosal integrity and energy absorption.

Mechanisms underlying therapeutic effects of DPP-4 inhibitor against ulcerative colitis in mice

AIM: To investigate the mechanisms underlying therapeutic effects of dipeptidyl peptidase-4 (DPP-4) inhibitor against ulcerative colitis in mice.

METHODS: Thirty male Balb/c mice were randomly divided into five groups: a normal group, an experimental colitis group, a DPP-4 inhibitor treatment group, a sulfasalazine (SASP) treatment group, and a DPP-4 inhibitor plus SASP treatment group. Ulcerative colitis was induced in mice with 5% dextran sulfate sodium. The normal group and experimental colitis group were intragastrically given 0.5% carboxymethyl cellulose (CMC), and the DPP-4 inhibitor group, SASP group and DPP-4 inhibitor plus SASP group were given sitagliptin, SASP, and both the two drugs once a day, respectively. Disease activity index (DAI) was assessed every day. After six days, all mice were sacrificed. Colonic pathological changes, myeloperoxidase (MPO) activity and serum levels of tumor necrosis factor-α (TNF-α), interleukin-10 (IL-10) and glucagon-like peptid-2 (GLP-2) were detected.

RESULTS: MPO activity and serum TNF-α level in the DPP-4 inhibitor group, SASP group and the combination group were significantly lower than those in the experimental colitis group (MPO activity: 1.20 U/g ± 0.19 U/g, 0.96 U/g ± 0.07 U/g, 0.81 U/g ± 0.06 U/g vs 1.81 U/g ± 0.23 U/g, all P < 0.01; 81.24 ng/L ± 9.12 ng/L, 67.86 ng/L ± 9.32 ng/L, 53.37 ng/L ± 9.08 ng/L vs 106.86 ng/L ± 17.02 ng/L, all P < 0.01). Serum GLP-2 level was significantly higher in the DPP-4 inhibitor group and the combination group than in the experimental group (55.07 pmol/L ± 4.43 pmol/L, 58.07 pmol/L ± 5.43 pmol/L vs 33.10 pmol/L ± 3.22 pmol/L, both P < 0.01). Serum IL-10 level was significantly higher in the SASP group and the combination group than in the experimental group (58.10 pg/mL ± 2.72 pg/mL, 60.68 pg/mL ± 2.35 pg/mL vs 38.20 pg/mL ± 2.61 pg/mL, both P < 0.01).

CONCLUSION: DPP-4 inhibitor has a synergistic effect with SASP possibly by exerting an anti-inflammatory effect and up-regulating serum level of GLP-2.

A pilot study examining the relationship among Crohn disease activity, glucagon-like peptide-2 signalling and intestinal function in pediatric patients

BACKGROUND⁄

OBJECTIVES

The relationship between the enteroendocrine hormone glucagon-like peptide 2 (GLP-2) and intestinal inflammation is unclear. GLP-2 promotes mucosal growth, decreases permeability and reduces inflammation in the intestine; physiological stimulation of GLP-2 release is triggered by nutrient contact. The authors hypothesized that ileal Crohn disease (CD) affects GLP-2 release.

METHODS

With ethics board approval, pediatric patients hospitalized with CD were studied; controls were recruited from local schools. Inclusion criteria were endoscopy-confirmed CD (primarily of the small intestine) with a disease activity index >150. Fasting and postprandial GLP-2 levels and quantitative urinary recovery of orally administered 3-O-methyl-glucose (active transport) and lactulose⁄mannitol (passive) were quantified during the acute and remission phases.

RESULTS

Seven patients (mean [± SD] age 15.3 ± 1.3 years) and 10 controls (10.3 ± 1.6 years) were studied. In patients with active disease, fasting levels of GLP-2 remained stable but postprandial levels were reduced. Patients with active disease exhibited reduced glucose absorption and increased lactulose⁄mannitol recovery; all normalized with disease remission. The change in the lactulose⁄mannitol ratio was due to both reduced lactulose and increased mannitol absorption.

CONCLUSIONS

These findings suggest that pediatric patients with acute ileal CD have decreased postprandial GLP-2 release, reduced glucose absorption and increased intestinal permeability. Healing of CD resulted in normalization of postprandial GLP-2 release and mucosal functioning (nutrient absorption and permeability), the latter due to an increase in mucosal surface area. These findings have implications for the use of GLP-2 and feeding strategies as a therapy in CD patients; further studies of the effects of inflammation and the GLP-2 axis are recommended.

Modern treatment of short bowel syndrome

PURPOSE OF REVIEW

Recently, the US Food and Drug Administration and the European Medicines Agency approved the glucagon-like peptide 2 analogue, teduglutide, for the treatment of short bowel syndrome (SBS), and this review describes the physiological basis for its clinical use.

RECENT FINDINGS

By affecting the intestinal neuroendocrine system, hormones may promote the growth of the intestinal mucosa, restore a more normal gastric emptying and secretion, stimulate intestinal blood flow, increase intestinal barrier function, immunity and absorption, and thereby promote structural and functional adaptation following intestinal resection. In a 3-week, phase 2, metabolic balance study, teduglutide increased intestinal wet weight absorption by ∼700 g/day and reduced faecal energy losses by ∼0.8 MJ/day. In two subsequent 24-week, phase 3 studies in SBS patients with intestinal failure (SBS-IF), teduglutide reduced the need for parenteral support in the same magnitude.

SUMMARY

Teduglutide adds incremental benefit to the limited medical treatment armamentarium in SBS patients. Modern treatments should aim to maximize remnant intestinal absorption, decrease malabsorption and accompanying symptoms, reduce the need, burdens and complications related to parenteral support, and ultimately improve the health-related quality of life in SBS-IF patients. Future research should target and implement other key hormones with similar effects, thereby promoting intestinal adaptation and rehabilitation in SBS patients.