Enzymatic- and renal-dependent catabolism of the intestinotropic hormone glucagon-like peptide-2 in rats

Long-term teduglutide associated with improved response in pediatric short bowel syndrome-associated intestinal failure

OBJECTIVES

Patients with short bowel syndrome-associated intestinal failure (SBS-IF) require long-term parenteral nutrition and/or intravenous fluids (PN/IV) to maintain fluid or nutritional balance. We report the long-term safety, efficacy, and predictors of response in pediatric patients with SBS-IF receiving teduglutide over 96 weeks.

METHODS

This was a pooled, post hoc analysis of two open-label, long-term extension (LTE) studies (NCT02949362 and NCT02954458) in children with SBS-IF. Endpoints included treatment-emergent adverse events (TEAEs) and clinical response (≥20% reduction in PN/IV volume from baseline). A multivariable linear regression identified predictors of teduglutide response; the dependent variable was mean change in PN/IV volume at each visit over 96 weeks.

RESULTS

Overall, 85 patients were analyzed; 78 patients received teduglutide in the parent and/or LTE studies (any teduglutide [TED] group), while seven patients did not receive teduglutide in either the parent or LTE studies. Most TEAEs were moderate or severe in intensity in both groups. By week 96, 82.1% of patients from the any TED group achieved a clinical response, with a mean fluid decrease of 30.1 mL/kg/day and an energy decrease of 21.6 kcal/kg/day. Colon-in-continuity, non-White race, older age at baseline, longer duration of teduglutide exposure, and increasing length of remaining small intestine were significantly associated with a reduction in mean PN/IV volume requirements.

CONCLUSIONS

In pediatric patients with SBS-IF, teduglutide treatment resulted in long-term reductions in PN/IV requirements. The degree of PN/IV volume reduction depended on the duration of teduglutide exposure, underlying bowel anatomy, and demographics.

Teduglutide improves liver chemistries in short bowel syndrome-associated intestinal failure: Post hoc analysis

BACKGROUND

Chronic hepatic complications are common in patients with short bowel syndrome-associated intestinal failure (SBS-IF). Teduglutide, a glucagon-like peptide-2 analogue, demonstrated efficacy in reducing parenteral nutrition and/or intravenous fluid dependence among patients with SBS-IF in phase 3 clinical studies.

METHODS

This was a post hoc analysis of pooled data from two separate randomized, double-blind, placebo-controlled, multinational phase 3 clinical studies. Adult patients with SBS-IF with parenteral nutrition and/or intravenous fluid dependence without liver disease at baseline were randomized to treatment with the glucagon-like peptide-2 analogue teduglutide (0.05 or 0.10 mg/kg/day) or placebo subcutaneously once daily for 24 weeks. Mixed-effects models assessed the baseline predictors of change in liver chemistries.

RESULTS

Between baseline and week 24, teduglutide treatment (n = 109) was associated with least squares mean reductions in aspartate aminotransferase (-7.51 IU/L; P = 0.014), alanine aminotransferase (-12.15 IU/L; P = 0.002), and bilirubin (-5.03 µmol/L [-0.057 mg/dl]; P < 0.001) compared with that of the placebo (n = 59). These values were independent of reductions in parenteral nutrition and/or intravenous fluid dependence.

CONCLUSION

Teduglutide treatment was associated with reductions in liver chemistries by week 24, which is beneficial for patients with SBS-IF beyond improvements in parenteral nutrition and/or intravenous fluid dependence. Future studies should examine how long-term teduglutide might mitigate the risk of liver disease in patients with SBS-IF.

Effect of feeding sodium butyrate to beef female cows during pre- and post-partum period on concentrations of glucagon-like peptides in plasma and colostrum

The objective of this study was to evaluate the effect of feeding beef cows with sodium butyrate during the late pregnancy and early post-partum periods on concentrations of glucagon-like peptide (GLP)-1 and 2 in plasma, colostrum, and transition milk. Twelve Japanese Black female cows were fed concentrate feed without (CON; n = 6) or with (BUTY; n = 6) sodium butyrate supplementation at 1.1% of dietary dry matter from -60 d relative to the expected parturition date to 4 d after parturition. Plasma total cholesterol concentration was higher for the BUTY than for the CON (P = 0.04). In addition, plasma GLP-1 concentration was higher for the BUTY than for the CON at 3 d after calving (P < 0.05). This study showed for the first time that GLP-1 is present in the colostrum of Japanese Black cows at higher concentrations as compared to in plasma (P < 0.01). On the other hand, no treatment effect was observed for concentrations of metabolite and hormone in colostrum and transition milk. In summary, feeding beef cows with sodium butyrate during the late gestation and early post-partum period likely increases plasma GLP-1 concentrations post-partum without affecting the components of colostrum and transition milk.

Long-acting agonists of human and rodent GLP-2 receptors for studies of the physiology and pharmacological potential of the GLP-2 system

BACKGROUND AND PURPOSE

Glucagon-like peptide-2 (GLP-2) is secreted postprandially from enteroendocrine Lcells and has anabolic action on gut and bone. Short-acting teduglutide is the only approved GLP-2 analog for the treatment of short-bowel syndrome (SBS). To improve the therapeutic effect, we created a series of lipidated GLP-2R agonists.

EXPERIMENTAL APPROACH

Six GLP-2 analogs were studied in vitro for cAMP accumulation, β-arrestin 1 and 2 recruitment, affinity, and internalization. The trophic actions on intestine and bone were examined in vivo in rodents.

KEY RESULTS

Lipidations at lysines introduced at position 12, 16, and 20 of hGLP-2(1-33) were well-tolerated with less than 2.2-fold impaired potency and full efficacy at the hGLP-2R in cAMP accumulation. In contrast, N- and C-terminal (His1 and Lys30) lipidations impaired potency by 4.2- and 45-fold and lowered efficacy to 77% and 85% of hGLP-2, respectively. All variants were similarly active on the rat and mouse GLP-2Rs and the three most active variants displayed increased selectivity for hGLP-2R over hGLP-1R activation, compared to native hGLP-2. Impact on arrestin recruitment and receptor internalization followed that of Gαs-coupling, except for lipidation in position 20, where internalization was more impaired, suggesting desensitization protection. A highly active variant (C16 at position 20) with low internalization and a half-life of 9.5 h in rats showed improved gut and bone tropism with increased weight of small intestine in mice and decreased CTX levels in rats.

CONCLUSION AND IMPLICATION

We present novel hGLP-2 agonists suitable for in vivo studies of the GLP-2 system to uncover its pharmacological potential.

Pharmacokinetics of Glepaglutide, A Long-Acting Glucagon-Like Peptide-2 Analogue: A Study in Healthy Subjects

BACKGROUND AND OBJECTIVE

Glepaglutide is a novel, long-acting, glucagon-like peptide-2 analogue in a stable aqueous formulation for subcutaneous dosing to treat patients with short bowel syndrome. This study was conducted primarily to characterise the pharmacokinetics of glepaglutide in healthy subjects.

METHODS

In this open-label, partially randomised, parallel-group study, healthy subjects were evenly randomised to glepaglutide 5 or 10 mg dosed subcutaneously once weekly for 6 weeks or to a single intravenous infusion of glepaglutide 1 mg. Each group comprised 15 subjects. Blood samples were drawn to determine plasma concentrations of the parent drug and its two main metabolites. Concentrations of glepaglutide were calculated as the sum of these three analytes. Citrulline was included as a pharmacodynamic biomarker. Safety was assessed throughout the study.

RESULTS

From a comparison of pharmacokinetic parameters following subcutaneous versus intravenous dosing, it is concluded that the pharmacokinetics of glepaglutide following subcutaneous dosing are primarily determined by slow release of the two main glepaglutide metabolites from a subcutaneous depot. For subcutaneous dosing once weekly, the two main metabolites accounted for >98% of the overall glepaglutide exposure at steady state, with the parent drug contributing to less than 1% of exposure. The estimated mean (95% confidence interval) effective half-life for glepaglutide 5 and 10 mg was 124 (73-185) h and 88 (31-146) h, respectively. There was an increase in the citrulline concentration for both glepaglutide subcutaneous dose levels. No safety issues were identified.

CONCLUSIONS

Slow release of active metabolites following subcutaneous dosing leads to a significantly protracted pharmacokinetic profile for glepaglutide. These results support that once- or twice-weekly subcutaneous dosing of glepaglutide could be an efficacious therapy for intestinal rehabilitation.

GOV IDENTIFIER

NCT03279302.

Short- versus Long-Term, Gender and Species Differences in the Intestinotrophic Effects of Long-Acting Glucagon-Like Peptide 2 Analog

Glucagon-like-peptide 2 (GLP-2) is an endogenous enteroendocrine physiological trophic peptide. Glepaglutide is a novel long-acting GLP-2 analog under development for the treatment of patients with Short Bowel Syndrome (SBS). The objective of this work was to compare the small intestinal trophic effects in both genders following short (1 week) versus long-term (26-39 weeks) GLP-2 treatment in Wistar rats and Beagle dogs. Following both short- and long-term treatment with glepaglutide, a significant dose-dependent intestinotrophic effect was seen in both genders and species. At all doses increased length and weight of the small intestine as well as macroscopic thickening and villous hypertrophy were noted in all segments of the small intestine, without any differences between genders. The findings were still present following a 6-week recovery period, indicating long-acting intestinotrophic effects of glepaglutide. These studies demonstrate that a long-acting GLP-2 analogue (glepaglutide) has a fast onset and long duration of intestinotrophic action with similar profile in both genders and species (rat and dog).

An updated overview of glucagon-like peptide-2 analog trophic therapy for short bowel syndrome in adults

Short bowel syndrome (SBS) is a clinical condition characterized by a failure to achieve optimal intestinal adaptation, which is necessary to maintain oral/enteral autonomy. At present, the treatment options for SBS are primarily intestinal replacement and rehabilitation. Intestinal rehabilitation mainly includes non-transplantation surgery and intestinal rehabilitation measures. In recent years, intestinal rehabilitation in patients with SBS using nutritional intestinal hormones, especially glucagon-like peptide-2 analogs, has made great progress. Many high-quality studies have provided evidence-based medical findings to support the development of clinical guidelines. This article reviews the latest research advancements regarding the use of glucagon-like peptide-2 analogs (teduglutide, glepaglutide, and apraglutide) in the treatment of SBS.

Glucagon-like peptide 2 (GLP-2) in bovine colostrum and transition milk

Bovine colostrum contains growth factors, cytokines, hormones, and enzymes, which have important roles in stimulating gastrointestinal development of neonatal calves. In the present study, we measured the concentration of glucagon-like peptide 2 (GLP-2), one of the gut-derived peptides secreted from intestinal L-cells, in colostrum and transition milk of Japanese black cattle. All colostrum samples were collected within 24 h after calving (d 0) and transition milk was collected at 24, 48 and 72 h relative to the time at colostrum sampling (d 1, d 2 and d 3, respectively). Concentrations of GLP-2 in colostrum were 5.53 ± 1.07 ng/mL on average (range = 0.94–9.60 ng/mL) and decreased from d 0 to 3 (P < 0.01). Furthermore, concentrations of GLP-2 in colostrum and transition milk were quadratically decreased with the elapsed time from parturition until colostrum sampling (R² = 0.48, P < 0.01). Our results show for the first time that GLP-2 is present in bovine colostrum and transition milk and that concentrations decreased with elapsed time from parturition.

The pivotal relation between glucagon-like peptides, NFκB and inflammatory bowel disease

Glucagon-like peptides (GLPs), GLP-1 and GLP-2, are released from intestinal enteroendocrine cells (L cells) in response to ingested nutrients. GLP-1 plays a crucial role in lowering blood glucose and controlling body weight, through stimulating the islet ß cells of pancreas to secrete insulin, inhibiting gastric emptying, and reducing food ingestion. Therefore, GLP-1 receptor agonists are now used in the treatment of obese patients with type 2 diabetes mellitus (T2DM). GLP-2, on the other hand, is used as a novel therapy for short bowel syndrome (SBS) through its ability to restore intestinal homeostasis and induce epithelial proliferation. GLPs and the inhibitors of their degradation enzymes, dipeptidyl peptidase-IV (DPP-IV) inhibitors, have many anti-inflammatory actions. Many animal-based clinical trials have proved that GLP-based therapy has a pivotal role in the management of inflammatory bowel disease (IBD), possibly through regulating the transcription factor nuclear factor kappa-ligand B (NFκB). NFκB controls the production and secretion of many cytokines and chemokines encountered in the pathophysiology of IBD such as interleukin (IL-1β-IL-12, IL-13, IL-21, IL-22, IL-6) and tumour necrosis factor-alpha (TNF-α) and hence, may provide a promising therapeutic option.

Insights into incretin-based therapies for treatment of diabetic dyslipidemia

Derangements in triglyceride and cholesterol metabolism (dyslipidemia) are major risk factors for the development of cardiovascular diseases in obese and type-2 diabetic (T2D) patients. An emerging class of glucagon-like peptide-1 (GLP-1) analogues and next generation peptide dual-agonists such as GLP-1/glucagon or GLP-1/GIP could provide effective therapeutic options for T2D patients. In addition to their role in glucose and energy homeostasis, GLP-1, GIP and glucagon serve as regulators of lipid metabolism. This review summarizes the current knowledge in GLP-1, glucagon and GIP effects on lipid and lipoprotein metabolism and frames the emerging therapeutic benefits of GLP-1 analogs and GLP-1-based multiagonists as add-on treatment options for diabetes associated dyslipidemia.

Site-Specific and Temporal Effects of Apraglutide, a Novel Long-Acting Glucagon-Like Peptide-2 Receptor Agonist, on Intestinal Growth in Mice

Long-acting glucagon-like peptide-2 receptor (GLP-2R) agonists are well-established to increase intestinal growth in rodents and, most notably, humans with short bowel syndrome. Most of the trophic effects of GLP-2R agonists are reported to be mediated through increased growth of the crypt-villus axis, resulting in enhanced mucosal mass and improved intestinal function. The present study examined the effects of apraglutide, a novel GLP-2R agonist, on the growth of the small intestine and colon after 3, 7, and 10 weeks of treatment in male and female mice. Apraglutide (3 mg/kg; three times per week) significantly increased small intestinal weight (P < 0.001) and length (P < 0.001) after 3 weeks of administration, with a further increase in effectiveness after 10 weeks (P < 0.01). Crypt depth and villus height were both markedly increased after 3 weeks of apraglutide administration (P < 0.001) but did not show any further increase with duration of treatment, whereas crypt number and intestinal circumference were increased after 7 and 10 weeks (P < 0.01) but not after 3 weeks of apraglutide treatment. Both the weight and the length of the colon were also enhanced by apraglutide treatment for 3 weeks (P < 0.001), and these effects were maintained but did not improve further with continued apraglutide administration. The results of this study demonstrate that the novel, long-acting GLP-2R agonist, apraglutide, demonstrates an unexpected marked ability to increase intestinal length as well as exert time- and location-dependent specificity in its intestinotrophic actions. SIGNIFICANCE STATEMENT: The novel long-acting glucagon-like peptide 2 receptor agonist, apraglutide, enhances intestinal weight as well as intestinal length in a time- and site-dependent fashion.

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

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

Effects of pulse-dose ruminal infusion of butyrate on plasma glucagon-like peptide 1 and 2 concentrations in dairy calves

Feeding of butyrate was found to have a positive effects in enhancing gut development and improving growth performance of calves. Equally, glucagon-like peptide 1 and 2 (GLP-1 and GLP-2), secreted from gastrointestinal L-cells in response to nutrient intake, were found to play a significant role in regulating blood glucose homeostasis and improving gut health. However, limited information is available about the relationship between butyrate and release of GLP-1 and GLP-2 in dairy calves. The objective of this study was to evaluate the effects of a pulse-dose ruminal infusion of butyrate on plasma GLP-1 and GLP-2 concentrations in dairy calves. Five ruminally cannulated mature Holstein bull calves (7.2 ± 0.10 mo, and 330 ± 16.0 kg of body weight; mean ± standard deviation) were used in a 5 × 5 Latin square with 4-d periods. On d 1 of each period at 0800 h, calves were ruminally infused with 1 of 5 treatments: 0 (saline), 0.3, 0.6, 0.9, and 1.2 g of butyrate per kg of body weight. Before butyrate infusion, calves were not offered feed overnight, and sequential blood and rumen fluid samples were taken before and after infusion on d 1 of each period. Ruminal butyrate and total volatile fatty acid concentrations increased linearly (2.65, 12.19, 20.99, 30.19, and 36.30; 23.68, 33.07, 40.94, 51.13, and 56.31 µmol/mL, for butyrate and total volatile fatty acids, respectively) in a dose-dependent manner, whereas propionate and isobutyrate increased quadratically. Ruminal and plasma butyrate, β-hydroxybutyrate, GLP-1, GLP-2, insulin, and glucose concentrations were all affected by treatment, time (except GLP-2), and interaction of treatment with time (except GLP-1). The area under the curve (AUC) summarized at different time points relative to the baseline (AUC30, AUC60, AUC120, and AUC240) for ruminal and plasma butyrate, and BHB, increased linearly with the dose of butyrate infused. However, AUC30, AUC60, AUC120, and AUC240 for plasma GLP-2 concentration were affected in a cubic manner unlike the linear effect on AUC30 and AUC60 for GLP-1. Plasma GLP-2 was not correlated with plasma butyrate (r = 0.16), GLP-1 (r = 0.03), or BHB (r = -0.05). This findings suggest that pulse-dosing of butyrate slightly increased both GLP-1 and GLP-2 concentrations at specific time points and this might be promoted by direct or indirect effect of butyrate on the intestinal L-cells.

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

CONTEXT

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

EVIDENCE ACQUISITION

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

EVIDENCE SYNTHESIS

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

CONCLUSION

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

Glucagon like peptide-2 and neoplasia; a systematic review

Glucagon like peptide-2 is synthesized from enteroendocrine L cells primarily located in the ileum and large intestine. GLP-2 stimulates crypt cell proliferation, increases intestinal blood flow, enhances gut barrier function, induces mucosal healing, and exerts an anti-apoptotic effect. Due to these effects GLP-2 is used in the treatment of short bowel syndrome (SBS). Areas covered: The aim of this systematic review was to provide information on the potential risk of intestinal neoplasia in patients receiving treatment with GLP-2. The literature search was performed independently by two authors in the following databases; Pubmed, Embase, Scopus, Web of Science and Cochrane. Expert commentary: This systematic review indicated that treatment with GLP-2(1-33) up to 30 months in humans without any known pre-existing cancer did not confer an increased risk of intestinal neoplasia in patients or animals. However, due to the small amount of patients studied it is premature to reach any final conclusions about GLP-2 - induced neoplasia. GLP-2(1-33) treatment in animals with a pre-induced cancer showed that GLP-2(1-33) may promote growth of existing neoplasia.

Response of plasma glucagon-like peptide-2 to feeding pattern and intraruminal administration of volatile fatty acids in sheep

Glucagon-like peptide-2 (GLP-2), a gut peptide secreted by enteroendocrine L cells, has recently been identified as a key regulator of intestinal growth and absorptive function in ruminants. However, reports on GLP-2 secretion are few, and more information regarding its secretion dynamics is needed. In this study, two experiments were conducted to elucidate the daily rhythm of GLP-2 secretion in response to feeding regimen and to investigate the effect of volatile fatty acids (VFA) on GLP-2 release in sheep. In experiment 1, blood samples were collected over 3 d from 4 Suffolk mature wethers adapted to a maintenance diet fed once daily; day 1 sampling was preceded by 24 h of fasting to reach steady state. On days 1 and 3, samples were collected every 10 min from 11:00 to 14:00 on both days and then every 1 h until 00:00 on day 1 only; feed was offered at 12:00. On day 2, feed was withheld, and sampling was performed every hour from 01:00 to 00:00. In experiment 2, 5 Suffolk mature wethers were assigned to 5 treatment groups of intraruminal administration of saline, acetate, propionate, butyrate, or VFA mix (acetate, propionate, and butyrate in a ratio of 65:20:15) in a 5 × 5 Latin square design. Blood samples were collected at 0, 1.5, 3, 6, 9, 12, 15, 20, 25, 30, 40, 50, 60, 90, and 120 min relative to the beginning of administration at 12:00. In both experiments, plasma GLP-2, glucagon-like peptide-1 (GLP-1), glucose, insulin, and β-hydroxy butyric acid (BHBA) levels were measured. In experiment 1, incremental area under the curve was greater (P < 0.05) post-feeding than pre-feeding on days 1 and 3 for GLP-2 and tended to be greater (P < 0.1) on day 1 for GLP-1. Plasma insulin, glucose, and BHBA levels increased (P < 0.05) on day 1 post-feeding. Plasma GLP-2 was poorly correlated with GLP-1 but positively correlated with insulin, glucose, and BHBA. In experiment 2, administration of butyrate and VFA mix remarkably increased plasma GLP-2 (P = 0.05) and BHBA (P < 0.0001) levels compared with those in other treatments. Plasma GLP-1 levels were higher with butyrate administration compared with those in the saline, acetate, and VFA mix (P = 0.019). Propionate administration increased plasma glucose (P = 0.013) and insulin (P = 0.053) levels. Thus, our data confirmed that GLP-2 release is responsive to feeding and might be promoted by BHBA produced by the rumen epithelial metabolism of butyrate. Further molecular- and cellular-level studies are needed to determine the role of butyrate as a signaling molecule for GLP-2 release.

Teduglutide for the Treatment of Short Bowel Syndrome

Objective:

To summarize the pharmacology, development, and clinical application of teduglutide (ALX-0600), a glucagon-like peptide-2 (GLP-2) analog for the treatment of short bowel syndrome (SBS).

Data Sources:

Clinical literature, including both primary sources and review articles, was accessed through a search of the MEDLINE databases (1980–March 2006). Key search terms included teduglutide, ALX-0600, glucagon-like peptide-2, short bowel syndrome, short gut, and intestinal adaptation. Clinical trial and drug data were supplied by the manufacturer, NPS Pharmaceuticals.

Study Selection and Data Extraction:

Review articles, abstracts, and clinical studies related to GLP-2 and its analog, teduglutide, were analyzed. An evaluation of the research exploring teduglutide for the management of SBS was conducted. Relevant information was then selected.

Data Synthesis:

Research has revealed that administration of GLP-2 to patients following major small bowel resection improves intestinal adaptation and nutrient absorption. Teduglutide is an enzyme-resistant GLP-2 analog that shows promise in preventing intestinal injury, restoring mucosal integrity, and enhancing intestinal absorptive function.

Conclusions:

Data from ongoing clinical trials indicate that teduglutide may have the ability to enhance intestinal absorptive capacity in patients with SBS. Further studies and the completion of Phase III trials are necessary to determine the appropriate dosage and length of treatment for patients with SBS to gain optimal therapeutic benefit from this drug.

Glucagon-like peptide 2 and its beneficial effects on gut function and health in production animals

Numerous endocrine cell subtypes exist within the intestinal mucosa and produce peptides contributing to the regulation of critical physiological processes including appetite, energy metabolism, gut function, and gut health. The mechanisms of action and the extent of the physiological effects of these enteric peptides are only beginning to be uncovered. One peptide in particular, glucagon-like peptide 2 (GLP-2) produced by enteroendocrine L cells, has been fairly well characterized in rodent and swine models in terms of its ability to improve nutrient absorption and healing of the gut after injury. In fact, a long-acting form of GLP-2 recently has been approved for the management and treatment of human conditions like inflammatory bowel disease and short bowel syndrome. However, novel functions of GLP-2 within the gut continue to be demonstrated, including its beneficial effects on intestinal barrier function and reducing intestinal inflammation. As knowledge continues to grow about GLP-2's effects on the gut and its mechanisms of release, the potential to use GLP-2 to improve gut function and health of food animals becomes increasingly more apparent. Thus, the purpose of this review is to summarize: (1) the current understanding of GLP-2's functions and mechanisms of action within the gut; (2) novel applications of GLP-2 (or stimulators of its release) to improve general health and production performance of food animals; and (3) recent findings, using dairy calves as a model, that suggest the therapeutic potential of GLP-2 to reduce the pathogenesis of intestinal protozoan infections.

The Pathogenesis of Resection-Associated Intestinal Adaptation

After massive small-bowel resection, the remnant bowel compensates by a process termed adaptation. Adaptation is characterized by villus elongation and crypt deepening, which increases the capacity for absorption and digestion per unit length. The mechanisms/mediators of this important response are multiple. The purpose of this review is to highlight the major basic contributions in elucidating a more comprehensive understanding of this process.

GLP2: an underestimated signal for improving glycaemic control and insulin sensitivity

Glucagon-like peptide 2 (GLP2) is a proglucagon-derived peptide produced by intestinal enteroendocrine L-cells and by a discrete population of neurons in the brainstem, which projects mainly to the hypothalamus. The main biological actions of GLP2 are related to the regulation of energy absorption and maintenance of mucosal morphology, function and integrity of the intestine; however, recent experimental data suggest that GLP2 exerts beneficial effects on glucose metabolism, especially in conditions related to increased uptake of energy, such as obesity, at least in the animal model. Indeed, mice lacking GLP2 receptor selectively in hypothalamic neurons that express proopiomelanocortin show impaired postprandial glucose tolerance and hepatic insulin resistance (by increased gluconeogenesis). Moreover, GLP2 acts as a beneficial factor for glucose metabolism in mice with high-fat diet-induced obesity. Thus, the aim of this review is to update and summarize current knowledge about the role of GLP2 in the control of glucose homeostasis and to discuss how this molecule could exert protective effects against the onset of related obesity type 2 diabetes.

Minor Contribution of Endogenous GLP-1 and GLP-2 to Postprandial Lipemia in Obese Men

Context

Glucose and lipids stimulate the gut-hormones glucagon-like peptide (GLP)-1, GLP-2 and glucose-dependent insulinotropic polypeptide (GIP) but the effect of these on human postprandial lipid metabolism is not fully clarified.

Objective

To explore the responses of GLP-1, GLP-2 and GIP after a fat-rich meal compared to the same responses after an oral glucose tolerance test (OGTT) and to investigate possible relationships between incretin response and triglyceride-rich lipoprotein (TRL) response to a fat-rich meal.

Design

Glucose, insulin, GLP-1, GLP-2 and GIP were measured after an OGTT and after a fat-rich meal in 65 healthy obese (BMI 26.5–40.2 kg/m²) male subjects. Triglycerides (TG), apoB48 and apoB100 in TG-rich lipoproteins (chylomicrons, VLDL₁ and VLDL₂) were measured after the fat-rich meal.

Main Outcome Measures

Postprandial responses (area under the curve, AUC) for glucose, insulin, GLP-1, GLP-2, GIP in plasma, and TG, apoB48 and apoB100 in plasma and TG-rich lipoproteins.

Results

The GLP-1, GLP-2 and GIP responses after the fat-rich meal and after the OGTT correlated strongly (r = 0.73, p<0.0001; r = 0.46, p<0.001 and r = 0.69, p<0.001, respectively). Glucose and insulin AUCs were lower, but the AUCs for GLP-1, GLP-2 and GIP were significantly higher after the fat-rich meal than after the OGTT. The peak value for all hormones appeared at 120 minutes after the fat-rich meal, compared to 30 minutes after the OGTT. After the fat-rich meal, the AUCs for GLP-1, GLP-2 and GIP correlated significantly with plasma TG- and apoB48 AUCs but the contribution was very modest.

Conclusions

In obese males, GLP-1, GLP-2 and GIP responses to a fat-rich meal are greater than following an OGTT. However, the most important explanatory variable for postprandial TG excursion was fasting triglycerides. The contribution of endogenous GLP-1, GLP-2 and GIP to explaining the variance in postprandial TG excursion was minor.

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.

Gut Peptides Are Novel Regulators of Intestinal Lipoprotein Secretion: Experimental and Pharmacological Manipulation of Lipoprotein Metabolism

Individuals with metabolic syndrome and frank type 2 diabetes are at increased risk of atherosclerotic cardiovascular disease, partially due to the presence of lipid and lipoprotein abnormalities. In these conditions, the liver and intestine overproduce lipoprotein particles, exacerbating the hyperlipidemia of fasting and postprandial states. Incretin-based, antidiabetes therapies (i.e., glucagon-like peptide [GLP]-1 receptor agonists and dipeptidyl peptidase-4 inhibitors) have proven efficacy for the treatment of hyperglycemia. Evidence is accumulating that these agents also improve fasting and postprandial lipemia, the latter more significantly than the former. In contrast, the gut-derived peptide GLP-2, cosecreted from intestinal L cells with GLP-1, has recently been demonstrated to enhance intestinal lipoprotein release. Understanding the roles of these emerging regulators of intestinal lipoprotein secretion may offer new insights into the regulation of intestinal lipoprotein assembly and secretion and provide new opportunities for devising novel strategies to attenuate hyperlipidemia, with the potential for cardiovascular disease reduction.

Acylation of Glucagon-like peptide-2: interaction with lipid membranes and in vitro intestinal permeability

Background

Acylation of peptide drugs with fatty acid chains has proven beneficial for prolonging systemic circulation as well as increasing enzymatic stability without disrupting biological potency. Acylation has furthermore been shown to increase interactions with the lipid membranes of mammalian cells. The extent to which such interactions hinder or benefit delivery of acylated peptide drugs across cellular barriers such as the intestinal epithelia is currently unknown. The present study investigates the effect of acylating peptide drugs from a drug delivery perspective.

Purpose

We hypothesize that the membrane interaction is an important parameter for intestinal translocation, which may be used to optimize the acylation chain length for intestinal permeation. This work aims to characterize acylated analogues of the intestinotrophic Glucagon-like peptide-2 by systematically increasing acyl chain length, in order to elucidate its influence on membrane interaction and intestinal cell translocation in vitro.

Results

Peptide self-association and binding to both model lipid and cell membranes was found to increase gradually with acyl chain length, whereas translocation across Caco-2 cells depended non-linearly on chain length. Short and medium acyl chains increased translocation compared to the native peptide, but long chain acylation displayed no improvement in translocation. Co-administration of a paracellular absorption enhancer was found to increase translocation irrespective of acyl chain length, whereas a transcellular enhancer displayed increased synergy with the long chain acylation.

Conclusions

These results show that membrane interactions play a prominent role during intestinal translocation of an acylated peptide. Acylation benefits permeation for shorter and medium chains due to increased membrane interactions, however, for longer chains insertion in the membrane becomes dominant and hinders translocation, i.e. the peptides get ‘stuck’ in the cell membrane. Applying a transcellular absorption enhancer increases the dynamics of membrane insertion and detachment by fluidizing the membrane, thus facilitating its effects primarily on membrane associated peptides.

Pharmacologic options for intestinal rehabilitation in patients with short bowel syndrome

A primary goal of intestinal rehabilitation programs is to facilitate intestinal adaptation. Adult patients with short bowel syndrome (SBS) who are dependent on parenteral nutrition and/or intravenous fluid (PN/IV) support have 2 hormonal pharmacologic treatment options available that may promote intestinal growth: a glucagon-like peptide 2 analog (teduglutide) and recombinant human growth hormone (somatropin). In two phase III clinical trials (N=169), 24 weeks of teduglutide administered to outpatients with SBS resulted in significant decreases in PN/IV volume requirements of 2.5-4.4 L/wk. In an extension study of one of these trials, patients with SBS who completed 30 months of teduglutide experienced a mean PN/IV reduction of 7.6 L/wk from baseline. Furthermore, some patients achieved independence from PN/IV support. The most common adverse events associated with teduglutide treatment in clinical trials were gastrointestinal symptoms, including abdominal distension, abdominal pain, and nausea. This safety profile is consistent with the associated underlying diseases leading to SBS or the known mechanism of action of teduglutide. A single phase III study (N=41) evaluated the safety and efficacy of a 4-week inpatient course of somatropin in combination with a glutamine-supplemented diet for adults with SBS. Somatropin treatment significantly reduced parenteral support requirements by 1.1 L/d in these patients. The most common adverse events were peripheral edema and musculoskeletal events. Large-scale, long-term follow-up studies of somatropin for SBS have not been conducted. Although treatment for patients with SBS must be individualized, teduglutide and somatropin are positive extensions to existing fluid and nutrient management strategies.

A randomized, double-blind, placebo-controlled, multiple-dose, parallel-group clinical trial to assess the effects of teduglutide on gastric emptying of liquids in healthy subjects

Background

Teduglutide, a recombinant analog of human glucagon-like peptide (GLP)-2, is a novel therapy recently approved for the treatment of adult patients with short bowel syndrome who are dependent on parenteral support. Previous studies assessing the effect of GLP-2 on gastric emptying in humans have yielded inconsistent results, with some studies showing no effect and others documenting a GLP-2–dependent delay in gastric emptying. The primary objective of this study was to assess the effect of teduglutide on gastric emptying of liquids in healthy subjects, as measured by the pharmacokinetics of acetaminophen.

Methods

This double-blind, parallel-group, single-center study enrolled and randomized 36 healthy subjects (22 men, 14 women) to receive subcutaneous doses of teduglutide 4 mg or placebo (2:1 ratio; 23:13) once daily on Days 1 through 10 in the morning. Gastric emptying of a mixed nutrient liquid meal was assessed by measuring acetaminophen levels predose and at 0.25, 0.5, 0.75, 1, 1.25, 1.5, 2, 3, 3.5, 4, 5, 6, 8, 10, 12, and 14 hours after administration of 1000 mg acetaminophen on Days 0 and 10. The primary study endpoint was a pharmacokinetic analysis of acetaminophen absorption in subjects receiving teduglutide or placebo.

Results

No significant differences in gastric emptying of liquids (acetaminophen area under the concentration [AUC] vs time curve from time 0 to the last measurable concentration, AUC extrapolated to infinity, maximum concentration [C_max], and time to C_max) were observed on Day 10 in subjects receiving teduglutide 4 mg versus subjects receiving placebo. There were no serious adverse events (AEs), deaths, or discontinuations due to an AE reported during the study.

Conclusions

Teduglutide 4 mg/day for 10 days does not affect gastric emptying of liquids in healthy subjects as measured by acetaminophen pharmacokinetics. No unexpected safety signals were observed.

Trial registration

This study was registered at ClinicalTrials.gov, identifier NCT01209351.

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.

Review article: a comparison of glucagon-like peptides 1 and 2

BACKGROUND

Recent advancements in understanding the roles and functions of glucagon-like peptide 1 (GLP-1) and 2 (GLP-2) have provided a basis for targeting these peptides in therapeutic strategies.

AIM

To summarise the preclinical and clinical research supporting the discovery of new therapeutic molecules targeting GLP-1 and GLP-2.

METHODS

This review is based on a comprehensive PubMed search, representing literature published during the past 30 years related to GLP-1 and GLP-2.

RESULTS

Although produced and secreted together primarily from L cells of the intestine in response to ingestion of nutrients, GLP-1 and GLP-2 exhibit distinctive biological functions that are governed by the expression of their respective receptors, GLP-1R and GLP-2R. Through widespread expression in the pancreas, intestine, nervous tissue, et cetera, GLP-1Rs facilitates an incretin effect along with effects on appetite and satiety. GLP-1 analogues resistant to degradation by dipeptidyl peptidase-IV and inhibitors of dipeptidyl peptidase-IV have been developed to aid treatment of diabetes and obesity. The GLP-2R is expressed almost exclusively in the stomach and bowel. The most apparent role for GLP-2 is its promotion of growth and function of intestinal mucosa, which has been targeted for therapies that promote repair and adaptive growth. These are used as treatments for intestinal failure and related conditions.

CONCLUSIONS

Our growing understanding of the biology and function of GLP-1, GLP-2 and corresponding receptors has fostered further discovery of fundamental biological function as well as new categories of potent therapeutic medicines.

Teduglutide reduces need for parenteral support among patients with short bowel syndrome with intestinal failure

BACKGROUND & AIMS

Teduglutide, a glucagon-like peptide 2 analogue, might restore intestinal structural and functional integrity by promoting growth of the mucosa and reducing gastric emptying and secretion. These factors could increase fluid and nutrient absorption in patients with short bowel syndrome with intestinal failure (SBS-IF). We performed a prospective study to determine whether teduglutide reduces parenteral support in patients with SBS-IF.

METHODS

We performed a 24-week study of patients with SBS-IF who were given subcutaneous teduglutide (0.05 mg/kg/d; n = 43) or placebo (n = 43) once daily. Parenteral support was reduced if 48-hour urine volumes exceeded baseline values by ≥ 10%. The primary efficacy end point was number of responders (patients with >20% reduction in parenteral support volume from baseline at weeks 20 and 24).

RESULTS

There were significantly more responders in the teduglutide group (27/43 [63%]) than the placebo group (13/43 [30%]; P = .002). At week 24, the mean reduction in parenteral support volume in the teduglutide group was 4.4 ± 3.8 L/wk (baseline 12.9 ± 7.8 L/wk) compared with 2.3 ± 2.7 L/wk (baseline 13.2 ± 7.4 L/wk) in the placebo group (P < .001). The percentage of patients with a 1-day or more reduction in the weekly need for parenteral support was greater in the teduglutide group (21/39 [54%]) than in the placebo group (9/39 [23%]; P = .005). Teduglutide increased plasma concentrations of citrulline, a biomarker of mucosal mass. The distribution of treatment-emergent adverse events that led to study discontinuation was similar between patients given teduglutide (n = 2) and placebo (n = 3).

CONCLUSIONS

Twenty-four weeks of teduglutide treatment was generally well tolerated in patients with SBS-IF. Treatment with teduglutide reduced volumes and numbers of days of parenteral support for patients with SBS-IF; ClinicalTrials.gov Number, NCT00798967.

Ghrelin, the proglucagon-derived peptides and peptide YY in nutrient homeostasis

Dysregulation of nutrient homeostasis is implicated in the current epidemics of obesity and type 2 diabetes mellitus. The maintenance of homeostasis in the setting of repeated cycles of feeding and fasting occurs through complex interactions between metabolic, hormonal and neural factors. Although pancreatic islets, the liver, muscle, adipocytes and the central nervous system are all key players in this network, the gastrointestinal tract is the first tissue exposed to ingested nutrients and thus has an important role. This Review focuses on several of the endocrine hormones released by the gastrointestinal tract prior to or during nutrient ingestion that have key roles in maintaining energy balance. These hormones include the gastric orexigenic hormone, ghrelin, and the distal L cell anorexigenic and metabolic hormones, glucagon-like peptide (GLP)-1, GLP-2, oxyntomodulin and peptide YY. Each of these hormones exerts a distinct set of biological actions to maintain nutrient homeostasis, the properties of which are currently, or might soon be, exploited in the clinic for the treatment of obesity and type 2 diabetes mellitus.

GLP2-2G-XTEN: a pharmaceutical protein with improved serum half-life and efficacy in a rat Crohn's disease model

OBJECTIVES

Glucagon-like peptide 2 (GLP2) is an intestinal growth factor that has been shown to stimulate intestinal growth and reduce disease severity in preclinical models of short bowel syndrome and inflammatory bowel disease. Teduglutide, a recombinant human GLP2 variant (GLP2-2G), has increased half-life and stability as compared to the native GLP2 peptide, but still requires twice daily dosing in preclinical models and daily dosing in the clinic. The goal of this study was to produce and characterize the preclinical pharmacokinetic and therapeutic properties of GLP2-2G-XTEN, a novel, long-acting form of GLP2-2G.

METHODOLOGY AND RESULTS

A GLP2-2G-XTEN fusion protein with extended exposure profile was produced by genetic fusion of GLP2-2G peptide to XTEN, a long, unstructured, non-repetitive, hydrophilic sequence of amino acids. The serum half-life of GLP2-2G-XTEN in mice, rats and monkeys was 34, 38 and 120 hours, respectively. Intestinotrophic effects were demonstrated in normal rats, where GLP2-2G-XTEN administration resulted in a significant increase in both small intestine weight and length. Efficacy of the GLP2-2G-XTEN protein was compared to that of GLP2-2G peptide in a rat Crohn's disease model, indomethacin-induced inflammation. Prophylactic administration of GLP2-2G-XTEN significantly increased the length, reduced the number of trans-ulcerations and adhesions, and reduced the TNFα content of the small intestine. GLP2-2G-XTEN demonstrated greater in vivo potency as compared to GLP2-2G peptide, and improvement in histopathology supported the GLP2-2G-XTEN treatment effects.

CONCLUSIONS AND SIGNIFICANCE

GLP2-2G-XTEN is intestinotrophic and demonstrates efficacy in a rat Crohn's disease model requiring a lower molar dose and less frequent dosing relative to GLP2-2G peptide. Allometric scaling based on pharmacokinetics from mouse, rat and monkey projects a human half-life of 240 hours. These improvements in preclinical pharmacokinetics and dosing indicate that GLP2-2G-XTEN may offer a superior therapeutic benefit for treatment of gastrointestinal diseases including Crohn's disease.

Enteral nutrients potentiate glucagon-like peptide-2 action and reduce dependence on parenteral nutrition in a rat model of human intestinal failure

Glucagon-like peptide-2 (GLP-2) is a nutrient-dependent, proglucagon-derived gut hormone that shows promise for the treatment of short bowel syndrome (SBS). Our objective was to investigate how combination GLP-2 + enteral nutrients (EN) affects intestinal adaption in a rat model that mimics severe human SBS and requires parenteral nutrition (PN). Male Sprague-Dawley rats were assigned to one of five groups and maintained with PN for 18 days: total parenteral nutrition (TPN) alone, TPN + GLP-2 (100 μg·kg(-1)·day(-1)), PN + EN + GLP-2(7 days), PN + EN + GLP-2(18 days), and a nonsurgical oral reference group. Animals underwent massive distal bowel resection followed by jejunocolic anastomosis and placement of jugular catheters. Starting on postoperative day 4, rats in the EN groups were allowed ad libitum access to EN. Groups provided PN + EN + GLP-2 had their rate of PN reduced by 0.25 ml/day starting on postoperative day 6. Groups provided PN + EN + GLP-2 demonstrated significantly greater body weight gain with similar energy intake and a safe 80% reduction in PN compared with TPN ± GLP-2. Groups provided PN + EN + GLP-2 for 7 or 18 days showed similar body weight gain, residual jejunal length, and digestive capacity. Groups provided PN + EN + GLP-2 showed increased jejunal GLP-2 receptor (GLP-2R), insulin-like growth factor-I (IGF-I), and IGF-binding protein-5 (IGFBP-5) expression. Treatment with TPN + GLP-2 demonstrated increased jejunal expression of epidermal growth factor. Cessation of GLP-2 after 7 days with continued EN sustained the majority of intestinal adaption and significantly increased expression of colonic proglucagon compared with PN + EN + GLP-2 for 18 days, and increased plasma GLP-2 concentrations compared with TPN alone. In summary, EN potentiate the intestinotrophic actions of GLP-2 by improving body weight gain allowing for a safe 80% reduction in PN with increased jejunal expression of GLP-2R, IGF-I, and IGFBP-5 following distal bowel resection in the rat.

Glucagon-like peptide-2 increases dysplasia in rodent models of colon cancer

The intestinal hormone, glucagon-like peptide-2 (GLP-2), enhances intestinal growth and reduces inflammation in rodent models. Hence, a degradation-resistant GLP-2 analog is under investigation for treatment of Crohn's disease. However, GLP-2 increases colonic dysplasia in murine azoxymethane (AOM)-induced colon cancer. Considering the increased colon cancer risk associated with chronic colitis, we have therefore examined the effects of long-acting hGly(2)GLP-2, as well as of endogenous GLP-2 using the antagonist hGLP-2(3-33) in two novel models of inflammation-associated colon cancer: rats fed the carcinogen 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and a high-fat diet (HFD) for one or three cycles, and mice with chronic dextran sodium-sulfate (DSS)-induced colitis administered AOM. hGly(2)GLP-2 treatment of one-cycle PhIP/HFD rats increased the number of colonic aberrant crypt foci by 72 ± 11% (P < 0.01). Fifty-one weeks after three PhIP/HFD cycles, hGly(2)GLP-2-treated rats had a 22% incidence of colon cancer, compared with 0% in vehicle-treated rats. AOM-DSS mice treated with vehicle or hGly(2)GLP-2 had high-grade dysplasia/colon cancer incidences of 56 and 64%, respectively, compared with 46% in hGLP-2(3-33)-treated AOM-DSS animals (P < 0.05). Unexpectedly, hGLP-2(3-33) also reduced the colitis damage score by 32.0 ± 8.4% (P < 0.05). All high-grade dysplastic/cancerous tumors had nuclear localization of β-catenin although β-catenin mRNA transcript and protein levels did not differ between treatment groups. GLP-2 receptor mRNA expression also was not different. However, hGLP-2(3-33)-treated mice had markedly reduced numbers of doublecortin-and-calmodulin-kinase-like-1-positive stem cells, by 73.7 ± 8.6% (P < 0.05). In conclusion, the results of this study indicate a role for hGly(2)GLP-2 and endogenous GLP-2 as potential cancer promoters in rodents.

Influence of acylation on the adsorption of GLP-2 to hydrophobic surfaces

Acylation of proteins with a fatty acid chain has proven useful for prolonging the plasma half-lives of proteins. In formulation of acylated protein drugs, knowledge about the effect of acylation with fatty acids on the adsorption behaviour of proteins at interfaces will be valuable. The aim of this work was to study the effect of acylation on the adsorption of GLP-2 from aqueous solution to a hydrophobic surface by comparing the adsorption of the 3766 Da GLP-2 with that of a GLP-2 variant acylated with a 16-carbon fatty acid chain through a β-alanine linker. Adsorption of GLP-2 and acylated GLP-2 were studied with isothermal titration calorimetry, fixed-angle optical reflectometry and total internal reflection fluorescence. Furthermore, the effect of acylation of GLP-2 on the secondary structure was studied with Far-UV CD. Acylation was observed to have several effects on the adsorption of GLP-2. Acylation increased the amount of GLP-2 adsorbing per unit surface area and decreased the initial adsorption rate of GLP-2. Finally, acylation increased the strength of the adsorption, as judged by the lower fraction desorbing upon rinsing with buffer.

Loss of glucagon-like peptide-2-induced proliferation following intestinal epithelial insulin-like growth factor-1-receptor deletion

BACKGROUND & AIMS

Glucagon-like peptide-2 (GLP-2) is an intestinal hormone that promotes growth of the gastrointestinal tract. Although insulin-like growth factor (IGF)-1 and the IGF-1 receptor (IGF-1R) are required for GLP-2-induced proliferation of crypt cells, little is known about localization of the IGF-1R which mediates the intestinotropic actions of GLP-2.

METHODS

We examined intestinal growth and proliferative responses in mice with conditional deletion of IGF-1R from intestinal epithelial cells (IE-igf1rKO) after acute administration (30-90 min) of GLP-2, in response to 24-hour fasting and re-feeding (to induce GLP-2-dependent adaptation), and after chronic exposure (10 days) to GLP-2.

RESULTS

IE-igf1rKO mice had normal small intestinal weight, morphometric parameters, proliferative indices, and distribution of differentiated epithelial cell lineages. Acute administration of GLP-2 increased nuclear translocation of β-catenin in non-Paneth crypt cells and stimulated the crypt-cell proliferative marker c-Myc in control but not IE-igf1rKO mice. Small intestinal weight, crypt depth, villus height, and crypt-cell proliferation were decreased in control and IE-igf1rKO mice after 24-hour fasting. Although re-feeding control mice restored all of these parameters, re-fed IE-igf1rKO mice had reductions in adaptive regrowth of the villi and crypt-cell proliferation. Control mice that were given chronic GLP-2 had increases in small intestinal weight, mucosal cross-sectional area, crypt depth, villus height, and crypt-cell proliferation. However, the GLP-2-induced increase in crypt-cell proliferation was not observed in IE-igf1rKO mice, and growth of the crypt-villus axis was reduced.

CONCLUSIONS

The proliferative responses of the intestinal epithelium to exogenous GLP-2 administration and conditions of GLP-2-dependent adaptive re-growth require the intestinal epithelial IGF-1R.

Teduglutide for the treatment of short bowel syndrome

Extensive resection of the intestine impairs its absorptive capacity and results in short bowel syndrome when the nutritional equilibrium is compromised. The remnant intestine adapts structurally to compensate, but nutritional autonomy cannot be achieved in patients with intestinal failure, requiring intravenous fluids and parenteral nutrition (PN) for sustenance of life. PN is expensive and associated with serious complications. Efforts to minimize or eliminate the need for PN heralded research focusing on the therapeutic utility of intrinsic gut factors involved in the postresection adaptation process. With the breakthrough recognition of the intestinotrophic properties of glucagon-like peptide-2, teduglutide, a recombinant analogue of glucagon-like peptide-2, is being investigated as a promising hope to mitigate the requirement of PN. Clinical studies to date have demonstrated a desirable benefit-to-risk profile in regards to its safety and efficacy. If approved for marketing, it will be the first of its class in short bowel syndrome management, offering an innovative therapeutic modality for this debilitating condition.

The "cryptic" mechanism of action of glucagon-like peptide-2

Glucagon-like peptide-2 (GLP-2) is a peptide hormone with multiple beneficial effects on the intestine, including expansion of the mucosal surface area through stimulation of crypt cell proliferation, as well as enhancement of nutrient digestion and absorption. Recent advances in clinical trials involving GLP-2 necessitate elucidation of the exact signaling pathways by which GLP-2 acts. In particular, the GLP-2 receptor has been localized to several intestinal cell types that do not include the proliferating crypt cells, and the actions of GLP-2 have thus been linked to a complex network of indirect mediators that induce diverse signaling pathways. The intestinotropic actions of GLP-2 on the colon have been shown to be mediated through the actions of keratinocyte growth factor and insulin-like growth factor (IGF)-2, whereas small intestinal growth has been linked to IGF-1, IGF-2, and ErbB ligands, as well as the IGF-1 receptor and ErbB. The cellular source of these mediators remains unclear, but it likely includes the intestinal subepithelial myofibroblasts. Conversely, the anti-inflammatory and blood flow effects of GLP-2 are dependent on vasoactive intestinal polypeptide released from submucosal enteric neurons and nitric oxide, respectively. Finally, recent studies have suggested that GLP-2 not only modulates intestinal stem cell behavior but may also promote carcinogenesis in models of sporadic colon cancer. Further consideration of the molecular cross-talk and downstream signaling pathways mediating the intestinotropic effects of GLP-2 is clearly warranted.

Enteroendocrine cells and lipid absorption

PURPOSE OF REVIEW

To examine recent papers linking enteroendocrine cells to lipid absorption.

RECENT FINDINGS

Specific inactivation of the proendocrine transcription factor neurogenin 3 (Ngn3) in the intestine leads to a loss of enteroendocrine cells, growth retardation, impaired lipid absorption and a high mortality during the weaning period. Furthermore, gain and loss of function experiments using mouse, hamster and primary enterocytes demonstrate that apoB-48-containing chylomicron formation and secretion may be regulated by enteroendocrine hormones. This seems to involve the multilineage scavenger receptor CD36, glycosylation of which is indirectly stimulated by enteroendocrine hormones.

SUMMARY

Hormones and peptides secreted by enteroendocrine cells are well known for their effect on food intake and appetite, the regulation of glucose homeostasis, gut motility, and various other physiological functions. What can now be added to this list is that they also influence lipid absorption, which opens up new opportunities to develop treatments for people suffering from overweight and its associated metabolic disorders.

Expression of mRNA for proglucagon and glucagon-like peptide-2 (GLP-2) receptor in the ruminant gastrointestinal tract and the influence of energy intake

Glucagon-like peptide-2 (GLP-2) is a potent trophic gut hormone, yet its function in ruminants is relatively unknown. Experiment 1 was conducted as a pilot study to establish the presence of GLP-2 in ruminants and to ascertain whether it was responsive to increased nutrition, as in non-ruminants. Concentrations of intact GLP-2 in the blood and gut epithelial mRNA expression of proglucagon (GCG) and the GLP-2 receptor (GLP2R) were measured in 4 ruminally, duodenally, and ileally cannulated steers. Steers were fed to meet 0.75 x NE(M) for 21 d, and then increased to 1.75 x NE(M) requirement for another 29 d. Blood samples and ruminal, duodenal, and ileal epithelium biopsies were collected at low intake (Days -6 and -3), acute high intake (Days 1 and 3), and chronic high intake (Days 7 and 29) periods. Experiment 2 investigated the mRNA expression pattern of GCG and GLP2R in epithelial tissue obtained from the forestomachs (rumen, omasum, and abomasum) and intestines (duodenum, jejunum, ileum, and colon) of 18 forage-fed Angus steers (260 kg BW). In Experiments 1 and 2, real-time polymerase chain reaction showed that expression of GCG and GLP2R mRNA was detectable in forestomach tissues, but expression was greater (P < 0.001) in small intestinal and colon tissue. High energy intake tended (P = 0.07) to increase plasma GLP-2 during the acute period and was paralleled by a 78% increase (P = 0.07) in ileal GCG mRNA expression. After this initial adaptation, duodenal GCG mRNA expression increased (P = 0.08) during the chronic high intake period. Duodenal GLP2R mRNA expression was not affected by energy intake, but ileal GLP2R expression was increased after 29 d of high energy intake compared to both the low and acute high intake periods (P = 0.001 and P = 0.01, respectively). These data demonstrate that cattle express GCG and GLP2R mRNA primarily in small intestinal and colon tissues. Increased nutrient intake increases ileal GCG mRNA and plasma GLP-2, suggesting that GLP-2 may play a role in the trophic response of the ruminant gastrointestinal tract to increased feed intake.

Growth factors: possible roles for clinical management of the short bowel syndrome

The structural and functional changes during intestinal adaptation are necessary to compensate for the sudden loss of digestive and absorptive capacity after massive intestinal resection. When the adaptive response is inadequate, short bowel syndrome (SBS) ensues and patients are left with the requirement for parenteral nutrition and its associated morbidities. Several hormones have been studied as potential enhancers of the adaptation process. The effects of growth hormone, insulin-like growth factor-1, epidermal growth factor, and glucagon-like peptide 2 on adaptation have been studied extensively in animal models. In addition, growth hormone and glucagon-like peptide 2 have shown promise for the treatment of SBS in clinical trials in human beings. Several lesser studied hormones, including leptin, corticosteroids, thyroxine, testosterone, and estradiol, are also discussed.

Carcinogenic effects of exogenous and endogenous glucagon-like peptide-2 in azoxymethane-treated mice

Glucagon-like peptide-2 (GLP-2) is a nutrient-dependent intestinotropic hormone that promotes intestinal growth, via increased intestinal proliferation and decreased apoptosis, as well as increases in nutrient absorption and barrier function. The long-acting analog h(Gly(2))GLP-2[1-33] is currently being tested for treatment of short bowel syndrome and Crohn's disease. However, the role of GLP-2 in colon carcinogenesis is controversial. To assess the intestinotropic effects of exogenous and endogenous GLP-2, C57BL6/J mice were injected with 1 microg h(Gly(2))GLP-2[1-33]; 30 or 60 ng hGLP-2[3-33], a GLP-2 receptor antagonist; or PBS (4 wk, twice a day, sc). Chronic h(Gly(2))GLP-2[1-33] increased small intestinal weight/body weight (P < 0.001), villus height (P < 0.001), crypt depth (P < 0.001), and crypt cell proliferation, as measured by expression of the proliferative marker Ki67 (P < 0.05-0.01). In contrast, chronic hGLP-2[3-33] decreased small intestinal weight/body weight (P < 0.05) and colon weight/body weight (P < 0.05). To assess the carcinogenic effects of endogenous and exogenous GLP-2, separate mice were injected with azoxymethane (10 mg/kg, 4 wk, every 7 d, ip), followed by 1.5 microg h(Gly(2))GLP-2[1-33], 30 ng hGLP-2[3-33], or PBS (4 wk, twice a day, sc) 2 or 12 wk thereafter. At 10 or 46 wk after azoxymethane treatment, the numbers of aberrant crypt foci increased with h(Gly(2))GLP-2[1-33] (P < 0.001) and decreased with hGLP-2[3-33] (P < 0.01-0.05) treatment. Furthermore, mucin-depleted aberrant foci, consistent with progressive dysplasia, were almost exclusively present in h(Gly(2))GLP-2[1-33]-treated mice (P < 0.01-0.001). Additionally, adenocarcinomas developed in h(Gly(2))GLP-2[1-33]-treated mice but not in those receiving hGLP-2[3-33] or PBS. Taken together, these studies indicate that chronic treatment with GLP-2 enhances colon carcinogenesis, whereas antagonism of the GLP-2 receptor decreases dysplasia, with possible implications for human therapy.