Glucagon-like peptide-2: update of the recent clinical trials

Evaluation of the Effectiveness of Teduglutide Treatment in Patients with Short Bowel Syndrome in Slovakia-Multicenter Real-World Study

(1) Background: We present the first real-world-data study on teduglutide-treated SBS patients in the Slovak Republic and the first study to enable the comparison of the effects of teduglutide treatment between the adult and pediatric populations. (2) Methods: This was a non-interventional retrospective cohort study of adult and pediatric SBS patients treated with teduglutide. Primary and secondary endpoints were the results of teduglutide use at 12 weeks and 6 months after the initiation of treatment, compared to baseline. (3) Results: Teduglutide treatment led to a statistically significant reduction in the volume of intravenous hydration, HPN caloric intake, HPN and intravenous hydration applications per week and to increased urine output in adult patients. The results in the pediatric population were similar, but not statistically significant. A complete weaning off HPN was achieved in 57.14% of all patients (50.00% of children; 62.50% of adults) after a median of 0.99 years of teduglutide treatment (1.07 and 0.98 years for children and adults, respectively). (4) Conclusions: Teduglutide treatment in SBS patients leads to considerable reduction in or even weaning off PN in both pediatric and adult patients.

ESPEN guideline on chronic intestinal failure in adults - Update 2023

BACKGROUND & AIMS

In 2016, ESPEN published the guideline for Chronic Intestinal Failure (CIF) in adults. An updated version of ESPEN guidelines on CIF due to benign disease in adults was devised in order to incorporate new evidence since the publication of the previous ESPEN guidelines.

METHODS

The grading system of the Scottish Intercollegiate Guidelines Network (SIGN) was used to grade the literature. Recommendations were graded according to the levels of evidence available as A (strong), B (conditional), 0 (weak) and Good practice points (GPP). The recommendations of the 2016 guideline (graded using the GRADE system) which were still valid, because no studies supporting an update were retrieved, were reworded and re-graded accordingly.

RESULTS

The recommendations of the 2016 guideline were reviewed, particularly focusing on definitions, and new chapters were included to devise recommendations on IF centers, chronic enterocutaneous fistulas, costs of IF, caring for CIF patients during pregnancy, transition of patients from pediatric to adult centers. The new guideline consist of 149 recommendations and 16 statements which were voted for consensus by ESPEN members, online in July 2022 and at conference during the annual Congress in September 2022. The Grade of recommendation is GPP for 96 (64.4%) of the recommendations, 0 for 29 (19.5%), B for 19 (12.7%), and A for only five (3.4%). The grade of consensus is "strong consensus" for 148 (99.3%) and "consensus" for one (0.7%) recommendation. The grade of consensus for the statements is "strong consensus" for 14 (87.5%) and "consensus" for two (12.5%).

CONCLUSIONS

It is confirmed that CIF management requires complex technologies, multidisciplinary and multiprofessional activity, and expertise to care for the underlying gastrointestinal disease and to provide HPN support. Most of the recommendations were graded as GPP, but almost all received a strong consensus.

Intestinal failure among adults and children: Similarities and differences

Intestinal failure (IF) is a complex medical condition that is caused by a constellation of disorders, resulting in the gut's inability to adequately absorb fluids and nutrients to sustain hydration, growth, and survival, thereby requiring the use of parenteral fluid and/or nutrition. Significant advancements in intestinal rehabilitation have resulted in improved survival rates for individuals with IF. There are distinct differences, however, related to etiology, adaptive potential and complications, and medical and surgical management when comparing children with adults. The purpose of this review is to contrast the similarities and differences between these two distinct groups and provide insight for future directions, as a growing population of pediatric patients will cross into the adult world for IF management.

Management of pediatric intestinal failure related to short bowel syndrome

Intestinal failure (IF) secondary to short bowel syndrome is a challenging and complex medical condition with significant risk for surgical and medical complications. Significant advancements in the care of this patient population have led to improved survival rates. Due to their intensive medical needs children with IF are at risk for long-term complications that require comprehensive management and close monitoring. The purpose of this paper is to review the available literature emphasizing the surgical aspects of care for children with IF secondary to short bowel syndrome. A key priority in the surgical care of this patient population includes strategies to preserve available bowel and maximize its function. Utilization of novel surgical techniques and autologous bowel reconstruction can have a significant impact on children with IF secondary to short bowel syndrome related to the function of their bowel and ability to achieve enteral autonomy. It is also important to understand the potential long-term complications to ensure strategies are put in place to mitigate risk with early detection to improve long-term outcomes.

N-terminal alterations turn the gut hormone GLP-2 into an antagonist with gradual loss of GLP-2 receptor selectivity towards more GLP-1 receptor interaction

BACKGROUND AND PURPOSE

To fully elucidate the regulatory role of the GLP-2 system in the gut and the bones, potent and selective GLP-2 receptor (GLP-2R) antagonists are needed. Searching for antagonist activity, we performed systematic N-terminal truncations of human GLP-2(1-33).

EXPERIMENTAL APPROACH

COS-7 cells were transfected with the human GLP-2R and assessed for cAMP accumulation or competition binding using ¹²⁵ I-GLP-2(1-33)[M10Y]. To examine selectivity, human GLP-1 or GIP receptor expressing COS-7 cells were assessed for cAMP accumulation.

KEY RESULTS

The affinity for the GLP-2R of the N-terminally truncated GLP-2 peptides decreased with reduced N-terminal peptide length (K_i 6.5-871 nM), while increasing antagonism appeared with inhibitory potencies (IC₅₀ ) values from 79 to 204 nM for truncation up to GLP-2(4-33) and then declined. In contrast, truncation-dependent increases in intrinsic activity were observed from an E_max of only 20% for GLP-(2-33) up to 46% for GLP-2(6-33) at 1 μM, followed by a decline. GLP-2(9-33) had the highest intrinsic efficacy (E_max 65%) and no antagonistic properties. Moreover, with truncations up to GLP-2(8-33) a gradual loss in selectivity for the GLP-2R appeared with increasing GLP-1 receptor (GLP-1R) inhibition (up to 73% at 1 μM). Lipidation of the peptides improved antagonism (IC₅₀ down to 7.9 nM) for both the GLP-2R and the GLP-1R.

CONCLUSION AND IMPLICATIONS

The N-terminus of GLP-2 is crucial for GLP-2R activity and selectivity. Our observations form the basis for the development of tool compounds for further characterization of the GLP-2 system.

Pharmacological strategies to enhance adaptation in intestinal failure

PURPOSE OF REVIEW

Intestinal failure because of more or less extensive resection of parts of the small and large intestine (short bowel syndrome) results from the reduction of absorptive surface of the remaining intestine and frequently results in dependence on parenteral nutrition. Parenteral nutrition, although lifesaving, is associated with short and long-term complications as well as with reduced quality of life and overall survival.

RECENT FINDINGS

Pharmacological enhancement of the physiological intestinal adaptive response by subcutaneous application of the glucagon-like peptide 2 analogue teduglutide results in an improved, hyperadaptive response. This is reflected by decreased parenteral calorie and fluid requirements, decreased parenteral nutrition infusion days per week including complete weaning off parenteral nutrition with complete oral autonomy, improved quality of life, and metabolic and nutritional stability.

SUMMARY

The advent of teduglutide as an authority-approved specific medication for intestinal failure in parenteral nutrition-dependent short bowel syndrome offers an effective and beneficial treatment for these patients. As a result, patients are more stable whether for medical or further surgical management including intestinal transplantation. Long-term efficacy and safety still have to be proven.

Landmark studies on the glucagon subfamily of GPCRs: from small molecule modulators to a crystal structure

The glucagon subfamily of class B G protein-coupled receptors (GPCRs) has been proposed to be a crucial drug target for the tretmaent of type 2 diabetes. The challenges associated with determining the crystal structures of class B GPCRs relate to their large amino termini and the lack of available small molecule ligands to stabilize the receptor proteins. Following our discovery of non-peptidic agonists for glucagon-like peptide-1 receptor (GLP-1R) that have therapeutic effects, we initiated collaborative efforts in structural biology and recently solved the three-dimensional (3D) structure of the human glucagon receptor (GCGR) 7-transmembrane domain, providing in-depth information about the underlying signaling mechanisms. In this review, some key milestones in this endeavor are highlighted, including discoveries of small molecule ligands, their roles in receptor crystallization, conformational changes in transmembrane domains (TMDs) upon activation and structure-activity relationship analyses.

Association of insulin resistance and GLP-2 secretion in obesity: a pilot study

OBJECTIVE

The objective of this pilot study was to determine whether glugagon-like peptide 2 (GLP-2) secretion relates to insulin sensitivity (IS) in obese subjects.

SUBJECTS AND METHODS

Twenty four obese subjects [body mass index (BMI) 40.0 ± 3.0 kg/m² (mean ± standard deviation)] were included, nine of which were male, age 43 ± 8 years. Twelve subjects had type 2 diabetes, all treated with oral anti-diabetic agents only. The subjects were submitted to standard meal tolerance test (MTT) for dosage of the curves: glucose, insulin, and GLP-2. Insulin sensitivity was measured by HOMA-IR, and OGIS was derived from the MTT. Spearman linear correlations and partial correlations were obtained.

RESULTS

There was an inverse relationship between the GLP-2 secretion and IS: HOMA-IR correlated with GLP-2 AUC (R = 0.504; p = 0.012), and OGIS correlated with GLP-2 incremental AUC (R = -0.54; p = 0.054). The correlation persisted after controlling for BMI.

CONCLUSION

We found an association of GLP-2 secretion and insulin resistance (IR). The understanding of the underlying mechanisms may provide future directions in the pharmacological manipulation of incretins, and in the treatment of obesity and related metabolic disorders.

Strategies for studying the ligand binding site of GPCRs: photoaffinity labeling of the VPAC1 receptor, a prototype of class B GPCRs

G protein-coupled receptors (GPCRs) are crucial receptors acting as molecular sensors for many physiological and pathological processes. Class B GPCRs represent a small GPCR subfamily encompassing 15 members, and are very promising targets for the development of drugs to improve many diseases such as chronic inflammation, neurodegeneration, diabetes, stress, and osteoporosis. Over the past decade, structure-function relationship studies have demonstrated that the N-terminal ectodomain (N-ted) of class B GPCRs plays a pivotal role in natural ligand recognition. The N-ted structure of some class B GPCRs folds into a Sushi domain consisting of two antiparallel β sheets stabilized by three disulfide bonds and a salt bridge. The VPAC1 receptor is an archetype of class B GPCRs that binds vasoactive intestinal peptide (VIP), a neuropeptide modulating many physiological processes. The structure-function relationship of VPAC1 has been extensively studied. The use of a photoaffinity labeling strategy has been a powerful approach to determine the physical contacts between the functional receptor and its ligand. Those studies, coupled with 3D molecular modeling techniques, have clearly demonstrated the crucial role of the VPAC1 receptor N-ted in VIP recognition.

Enteroendocrine cells in terminal ileal Crohn's disease

BACKGROUND AND AIMS

Enteroendocrine cells sense gut luminal contents, and orchestrate digestive physiology whilst contributing to mucosal homeostasis and innate immunity. The terminal ileum is the key site of EEC expression but detailed assessment of their subtypes, lineage transcription factors and expression products has not been undertaken in terminal ileal Crohn's disease. Recent Crohn's disease gene wide association studies have linked the neuroendocrine transcription factor Phox2b; while autoantibodies to an enteroendocrine protein, ubiquitination protein 4a, have been identified as a disease behaviour biomarker.

METHODS

Terminal ileal tissue from small or large bowel Crohn's disease and normal controls was analysed for enteroendocrine marker expression by immunohistochemistry and quantitative polymerase chain reaction. Inflammation was graded by endoscopic, clinical, histological and biochemical scoring.

RESULTS

In small bowel disease, glucagon-like peptide 1 and chromogranin A cells were increased 2.5-fold (p=0.049) and 2-fold (p=0.031) respectively. Polypeptide YY cells were unchanged. Ileal enteroendocrine cell expression was unaffected in the presence of Crohn's colitis. Phox2b was co-localised to enteroendocrine cells and showed a 1.5-fold increase in ileal disease. Significant mRNA increases were noted for chromogranin A (3.3-fold; p=0.009), glucagon-like peptide 1 (3.1-fold; p=0.007) and ubiquitination protein 4a (2.2-fold; p=0.02). Neurogenin 3, an enteroendocrine transcription factor showed ~2 fold-upregulation (p=0.048).

CONCLUSIONS

Enhanced enteroendocrine cell activity is present in small bowel disease, and observed in restricted cell lineages. This may impact on the epithelial immune response, cellular homeostasis and nutrient handling and influence appetite via increased satiety signalling in the gut-brain axis.

[Short bowel syndrome in children: a diagnosis and management update]

Short bowel syndrome (SBS) refers to the sum of the functional alterations that are the result of a critical reduction in the length of the intestine, which in the absence of adequate treatment, presents as chronic diarrhea, chronic dehydration, malnutrition, weight loss, nutriment and electrolyte deficiency, along with a failure to grow that is present with greater frequency during the neonatal period. The aim was to carry out a review of the literature encompassing the definition and the most frequent causes of SBS, together with an understanding of its physiopathology, prognostic factors, and treatment. An Internet search of PubMed articles was carried out for the existing information published over the last 20 years on SBS in children, using the keywords "short bowel syndrome". From a total of 784 potential articles, 82 articles were chosen for the literature review. The treatment of patients presenting with SBS is quite a challenge and therefore it is necessary to establish multidisciplinary management with a focus on maintaining optimal nutritional support that covers the necessities of growth and development and at the same time provides a maximum reduction of short, medium, and long-term complications. The diagnosis and treatment of a child with SBS require a team of professionals that are experts in gastroenterologic, pediatric, and nutritional management. The outcome for the child will be directly related to opportune management, as well as to the length of the intestinal resection and the presence or absence of the ileocecal valve.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

VPAC receptors: structure, molecular pharmacology and interaction with accessory proteins

The vasoactive intestinal peptide (VIP) is a neuropeptide with wide distribution in both central and peripheral nervous systems, where it plays important regulatory role in many physiological processes. VIP displays a large biological functions including regulation of exocrine secretions, hormone release, fetal development, immune responses, etc. VIP appears to exert beneficial effect in neuro-degenerative and inflammatory diseases. The mechanism of action of VIP implicates two subtypes of receptors (VPAC1 and VPAC2), which are members of class B receptors belonging to the super-family of GPCR. This article reviews the current knowledge regarding the structure and molecular pharmacology of VPAC receptors. The structure-function relationship of VPAC1 receptor has been extensively studied, allowing to understand the molecular basis for receptor affinity, specificity, desensitization and coupling to adenylyl cyclase. Those studies have clearly demonstrated the crucial role of the N-terminal ectodomain (N-ted) of VPAC1 receptor in VIP recognition. By using different approaches including directed mutagenesis, photoaffinity labelling, NMR, molecular modelling and molecular dynamic simulation, it has been shown that the VIP molecule interacts with the N-ted of VPAC1 receptor, which is itself structured as a 'Sushi' domain. VPAC1 receptor also interacts with a few accessory proteins that play a role in cell signalling of receptors. Recent advances in the structural characterization of VPAC receptor and more generally of class B GPCRs will lead to the design of new molecules, which could have considerable interest for the treatment of inflammatory and neuro-degenerative diseases.

Efficacy of the glucagon-like peptide-1 agonist exenatide in the treatment of short bowel syndrome

BACKGROUND

Short bowel syndrome (SBS) is a serious clinical disorder characterized by diarrhea and nutritional deprivation. Glucagon-like peptide-1 (GLP-1) is a key hormone, produced by L-cells in the ileum, that regulates proximal gut transit. When extensive ileal resection occurs, as in SBS, GLP-1 levels may be deficient. In this study, we test whether the use of GLP-1 agonist exenatide can improve the nutritional state and intestinal symptoms of patients with SBS.

METHODS

Five consecutive patients with SBS based on ≤90 cm of small bowel and clinical evidence of nutritional deprivation were selected. Baseline SBS symptoms, demographic and laboratory data were obtained. Antroduodenal manometry was performed on each subject. Each patient was then started on exenatide and over the following month, the baseline parameters were repeated.

KEY RESULTS

The subjects consisted of four males and one female, aged 46-69 years. At baseline, all had severe diarrhea that ranged from 6 to 15 bowel movements per day, often occurring within minutes of eating. After exenatide, all five patients had immediate improvement in bowel frequency and form; bowel movements were no longer meal-related. Total parenteral nutrition was stopped successfully in three patients. Antroduodenal manometry revealed continuous low amplitude gastric contractions during fasting which completely normalized with exenatide.

CONCLUSIONS & INFERENCES

Exenatide is a novel and safe treatment option for SBS. It produced substantial improvement in the bowel habits, nutritional status and quality of life of SBS patients. Successful treatment with exenatide may significantly reduce the need for parenteral nutrition and small bowel transplant.

Short bowel syndrome: a review of management options

Extensive resection of the intestinal tract frequently results in inadequate digestion and/or absorption of nutrients, a condition known as short bowel syndrome (SBS). This challenging condition demands a dedicated multidisciplinary team effort to overcome the morbidity and mortality in these patients. With advances in critical care management, more and more patients survive the immediate morbidity of massive intestinal resection to present with SBS. Several therapies, including parenteral nutrition (PN), bowel rehabilitation and surgical procedures to reconstruct bowel have been used in these patients. Novel dietary approaches, pharmacotherapy and timely surgical interventions have all added to the improved outcome in these patients. However, these treatments only partially correct the underlying problem of reduced bowel function and have limited success resulting in 30% to 50% mortality rates. However, increasing experience and encouraging results of intestinal transplantation has added a new dimension to the management of SBS. Literature available on SBS is exhaustive but inconclusive. We conducted a review of scientific literature and electronic media with search terms 'short bowel syndrome, advances in SBS and SBS' and attempted to give a comprehensive account on this topic with emphasis on the recent advances in its management.

Role of cholinergic neurons in the motor effects of glucagon-like peptide-2 in mouse colon

Glucagon-like peptide-2 (GLP-2) reduces mouse gastric tone and small intestine transit, but its action on large intestine motility is still unknown. The purposes of the present study were 1) to examine the influence of GLP-2 on spontaneous mechanical activity and on neurally evoked responses, by recording intraluminal pressure from mouse isolated colonic segments; 2) to characterize GLP-2 mechanism of action; and 3) to determine the distribution of GLP-2 receptor (GLP-2R) in the mouse colonic muscle coat by immunohistochemistry. Exogenous GLP-2 (0.1-300 nM) induced a concentration-dependent reduction of the spontaneous mechanical activity, which was abolished by the desensitization of GLP-2 receptor or by tetrodotoxin, a voltage-dependent Na(+)-channel blocker. GLP-2 inhibitory effect was not affected by N(ω)-nitro-l-arginine methyl ester (a nitric oxide synthase inhibitor), apamin (a blocker of small conductance Ca(2+)-dependent K(+) channels), or [Lys1,Pro2,5,Arg3,4,Tyr6]VIP(7-28) (a VIP receptor antagonist), but it was prevented by atropine or pertussis toxin (PTX), a G(i/o) protein inhibitor. Proximal colon responses to electrical field stimulation were characterized by nitrergic relaxation, which was followed by cholinergic contraction. GLP-2 reduced only the cholinergic evoked contractions. This effect was almost abolished by GLP-2 receptor desensitization or PTX. GLP-2 failed to affect the contractile responses to exogenous carbachol. GLP-2R immunoreactivity (IR) was detected only in the neuronal cells of both plexuses of the colonic muscle coat. More than 50% of myenteric GLP-2R-IR neurons shared the choline acetyltransferase IR. In conclusion, the activation of GLP-2R located on cholinergic neurons may modulate negatively the colonic spontaneous and electrically evoked contractions through inhibition of acetylcholine release. The effect is mediated by G(i) protein.

VPAC1 receptor binding site: contribution of photoaffinity labeling approach

The vasoactive intestinal peptide (VIP) is a prominent 28 aminoacid neuropeptide with wide distribution in both central and peripheral nervous systems, where it plays important regulatory role in many physiological processes. VIP has a large spectrum of biological functions including exocrine secretions, hormone release, foetal development, immune response and also exerts beneficial effect in neuro-degenerative and inflammatory diseases. Few years ago, it has been shown that VIP can be a promising anti-inflammatory agent. VIP mechanisms of action implicate two sub-types of receptors (VPAC1 and VPAC2) which are members of class B receptors belonging to the super-family of G protein-coupled receptor (GPCR). Because, VPAC1 receptor plays an important role in the modulation of the ant-inflammatory response and represent an archetype of class B GPCR, we have extensively studied the structure-function relationship of this receptor, which allowed us to define the molecular basis of that receptor in term of affinity, specificity, desensitization and coupling to adenylyl cyclase. Those studies showed the crucial role of the N-terminal ectodomain (N-ted) of VPAC1 receptor in VIP binding. Using different techniques including photoaffinity labeling, NMR, molecular modeling and molecular dynamic simulation, it has been possible to define how VIP interacts with its receptor. We have shown that most of the VIP molecule, 1-28 (alpha-helix) sequence, tightly binds the N-ted part of the receptor which is himself structured as a <<Sushi>> domain. In contrast, the N-terminal part of the specific antagonist PG97-269 is in physical contact with the N-ted but in different region. These studies define the molecular mechanism implicated in the activation of class B VPAC1 receptor and should allow the development of new VIP pharmacology using rational synthesis of agonist molecules.

Glucagon-like peptide-2 modulates neurally evoked mucosal chloride secretion in guinea pig small intestine in vitro

Glucagon-like peptide-2 (GLP-2) is an important neuroendocrine peptide in intestinal physiology. It influences digestion, absorption, epithelial growth, motility, and blood flow. We studied involvement of GLP-2 in intestinal mucosal secretory behavior. Submucosal-mucosal preparations from guinea pig ileum were mounted in Ussing chambers for measurement of short-circuit current (I(sc)) as a surrogate for chloride secretion. GLP-2 action on neuronal release of acetylcholine was determined with ELISA. Enteric neuronal expression of the GLP-2 receptor (GLP-2R) was studied with immunohistochemical methods. Application of GLP-2 (0.1-100 nM) to the serosal or mucosal side of the preparations evoked no change in baseline I(sc) and did not alter transepithelial ionic conductance. Transmural electrical field stimulation (EFS) evoked characteristic biphasic increases in I(sc), with an initially rapid rising phase followed by a sustained phase. Application of GLP-2 reduced the EFS-evoked biphasic responses in a concentration-dependent manner. The GLP-2R antagonist GLP-2-(3-33) significantly reversed suppression of the EFS-evoked responses by GLP-2. Tetrodotoxin, scopolamine, and hexamethonium, but not vasoactive intestinal peptide type 1 receptor (VPAC1) antagonist abolished or reduced to near zero the EFS-evoked responses. GLP-2 suppressed EFS-evoked acetylcholine release as measured by ELISA. Pretreatment with GLP-2-(3-33) offset this action of GLP-2. In the submucosal plexus, GLP-2R immunoreactivity (-IR) was expressed in choline acetyltransferase-IR neurons, somatostatin-IR neurons, neuropeptide Y-IR neurons, and vasoactive intestinal peptide-IR neurons. We conclude that submucosal neurons in the guinea pig ileum express GLP-2R. Activation of GLP-2R decreases neuronally evoked epithelial chloride secretion by suppressing acetylcholine release from secretomotor neurons.

The effect of a high-MUFA, low-glycaemic index diet and a low-fat diet on appetite and glucose metabolism during a 6-month weight maintenance period

We aimed to test the effects of three different weight maintenance diets on appetite, glucose and fat metabolism following an initial low-energy diet (LED) induced body weight loss. Following an 8-week LED and a 2-3-week refeeding period, 131 subjects were randomized to three diets for 6 months: MUFA, moderate-fat (35-45 energy percentage (E%) fat), high in MUFA with low glycaemic index; LF, low fat (20-30 E% fat) or CTR, control (35 E% fat). A meal test study was performed in a subgroup, before and after the 6-month dietary intervention, with forty-two subjects completing both meal tests. No difference in body weight, energy intake or appetite ratings were observed between diets. Both the LF and MUFA diets compared to CTR diet reduced postprandial glycaemia and insulinaemia and lowered fasting insulin from month 0 to month 6. Following the 8-week LED period lower levels of the appetite regulating peptides, pancreatic polypeptide, peptide YY, glucagon-like peptide-1 and glucagon-like peptide-2, along with increased appetite scores were seen in comparison to measurements performed after the 6-month dietary intervention. In conclusion, the two competing diets, MUFA and LF, were equally good with respect to glucose metabolism, whereas the CTR diet resembling the typical Western diet, high in SFA, sugar and high glycaemic carbohydrates, indicated associations to lowering of insulin sensitivity. Lower levels of appetite regulatory peptides along with increased appetite scores following an 8-week LED and 2-3-week refeeding period, suggest that strategies for physiological appetite control following a LED period are needed, in order to prevent weight regain.

Exogenous glucagon-like peptide-2 (GLP-2) augments GLP-2 receptor mRNA and maintains proglucagon mRNA levels in resected rats

BACKGROUND

Glucagon-like peptide-2 (GLP-2) is a nutrient-dependent proglucagon-derived hormone that stimulates intestinal adaptive growth. Our aim was to determine whether exogenous GLP-2 increases resection-induced adaptation without diminishing endogenous proglucagon and GLP-2 receptor expression.

METHODS

Rats underwent transection or 70% jejunoileal resection +/- GLP-2 infusion (100 microg/kg body weight/d) and were fed a semipurified diet with continuous infusion of GLP-2 or saline by means of jugular catheter. After 7 days, body weight, mucosal cellularity (dry mass, protein and DNA), crypt-villus height, and crypt cell proliferation (by bromodeoxyuridine staining) were determined. Plasma bioactive GLP-2 (by radioimmunoassay), proglucagon and GLP-2 receptor mRNA expression (by Northern blot and real-time reverse transcriptase quantitative polymerase chain reaction) were measured. GLP-2 receptor was colocalized to neuroendocrine markers by immunohistochemistry.

RESULTS

Low-dose exogenous GLP-2 increased mucosal cellularity and crypt-villus height in the duodenum, jejunum, and ileum; enterocyte proliferation in the jejunal crypt; and duodenal and jejunal sucrase segmental activity. Plasma bioactive GLP-2 concentration increased 70% upon resection, with an additional 54% increase upon GLP-2 infusion in resected rats (P < .05). Ileal proglucagon mRNA expression increased with resection, and exogenous ileum GLP-2 failed to blunt this response. Exogenous GLP-2 increased ileum GLP-2 receptor expression 3-fold in resected animals and was colocalized to vasoactive intestinal peptide-positive and endothelial nitric oxide synthase-expressing enteric neurons and serotonin-containing enteroendocrine cells in the jejunum and ileum of resected rats.

CONCLUSIONS

Exogenous GLP-2 augments adaptive growth and digestive capacity of the residual small intestine in a rat model of mid-small bowel resection by increasing plasma GLP-2 concentrations and GLP-2 receptor expression without diminishing endogenous proglucagon expression.

Class-B GPCR activation: is ligand helix-capping the key?

The class B family of G-protein-coupled receptors (GPCRs) regulates essential physiological functions such as exocrine and endocrine secretions, feeding behaviour, metabolism, growth, and neuro- and immuno-modulations. These receptors are activated by endogenous peptide hormones including secretin, glucagon, vasoactive intestinal peptide, corticotropin-releasing factor and parathyroid hormone. We have identified a common structural motif that is encoded in all class B GPCR-ligand N-terminal sequences. We propose that this local structure, a helix N-capping motif, is formed upon receptor binding and constitutes a key element underlying class B GPCR activation. The folded backbone conformation imposed by the capping structure could serve as a template for a rational design of drugs targeting class B GPCRs in several diseases.

The alpha cell expresses glucagon-like peptide-2 receptors and glucagon-like peptide-2 stimulates glucagon secretion from the rat pancreas

AIMS/HYPOTHESIS

Glucagon-like peptide-2 (GLP-2) is a gut hormone regulating intestinal growth and nutrient absorption. Recently, GLP-2 has been reported to stimulate glucagon secretion in healthy humans. We sought to clarify the mechanism and physiological significance of this endocrine effect.

MATERIALS AND METHODS

The expression of the GLP-2 receptor gene, Glpr2, and the localisation of the protein were evaluated by real-time PCR on cDNA from isolated rat islets and by immunohistochemistry in rat and human pancreas. The glucagon, insulin and somatostatin responses to 0.1, 1 and 10 nmol/l GLP-2 and to GLP-1 and GLP-2 given simultaneously were studied in the isolated perfused rat pancreas.

RESULTS

Expression of Glp2r transcript was confirmed by PCR. In both human and rat pancreas, GLP-2r immunoreactivity was colocalised with proglucagon. GLP-2 at 10 nmol/l increased glucagon secretion significantly from a pre-infusion level of 0.314 +/- 0.07 to 0.508 +/- 0.09 pmol/min (p < 0.0005), whereas lower GLP-2 concentrations were ineffective. Neither insulin nor somatostatin output was influenced. During simultaneous administration of GLP-1 and GLP-2, net glucagon release was no longer reduced by 0.1, 1 or 10 nmol/l GLP-1, which, when given alone, inhibited glucagon secretion by 25.0 +/- 9.9, 46.2 +/- 4.8, and 44.1 +/- 2.9%, respectively.

CONCLUSIONS/INTERPRETATION

Our results suggest that GLP-2 stimulates glucagon secretion through GLP-2r present on the alpha cell in rats. In the presence of GLP-2, the glucagonostatic effect of GLP-1, normally co-secreted with GLP-2, is markedly inhibited. Based on our analogous immunohistochemical findings in human pancreas, this mechanism also applies in all likelihood to humans. However, further in vivo studies are required to assess the physiological significance of the glucagonotropic action of GLP-2 in humans.

Intestinal epithelial cell proliferation is dependent on the site of massive small bowel resection

Early intestinal adaptation after massive small bowel resection (SBR) is driven by increased epithelial cell (EC) proliferation. There is a clear clinical difference in the post-operative course of patients after the loss of proximal (P) compared to distal (D) small bowel. This study examined the effects of the site of SBR on post-resectional intestinal adaptation, and investigated the potential mechanisms involved. C57BL/6J mice (n = 7/group) underwent: (1) 60% P-SBR, (2) 60% D-SBR, (3) 60% mid (M)-SBR and (4) SHAM-operation (transection/reanastomosis). Mice were sacrificed at 7 days after surgery and ECs and adjacent mucosal lymphocytes (IELs) isolated. Adaptation was assessed in both jejunum and ileum by quantification of villus height, crypt depth, villus cell size, crypt cell size (microns), goblet cell number, and EC proliferation (%BrdU incorporation). Proliferation signalling pathways including keratinocyte growth factor (KGF)/KGFR(1), IL-7/IL-7R, and epidermal growth factor receptor (EGFR) were measured by RT-PCR. Expression of IL-7 was further analysed by immunofluorescence. Data were analyzed using ANOVA. All three SBR models led to significant increases in villus height, crypt depth, goblet cell numbers and EC proliferation rate when compared to respective SHAM groups. The strongest morphometric changes were found for jejunal segments after M-SBR and for ileal segments after P-SBR. Furthermore, morphometric analysis showed that at 1-week post-resection a tremendous increase in EC numbers occurred in jejunal villi (cell hyperplasia), whereas a significant increase in EC size predominated in ileal villi (cell hypertrophy). mRNA expression of KGF, KGFR(1), IL-7R, and EGFR showed a significant increase only after D-SBR, whereas IL-7 increased significantly after SBR in all investigated models, and this was confirmed by immunofluorescence studies. Early intestinal adaptation shows distinct differences depending on the site of SBR, and is predominately driven by cell hyperplasia in jejunal villi and cell hypertrophy in ileal villi. However, the exact mechanisms, which guide these signalling pathways are still unclear.

Nutritional management of infants with short bowel syndrome

The prevalence of short bowel syndrome appears to be increasing because of more aggressive surgical and medical approaches to the management of neonatal intraabdominal catastrophies. Hence, a large cohort of neonates with intestinal failure occupies neonatal intensive care units, requiring chronic total parenteral nutrition (TPN) in hopes that the residual bowel will adapt, thereby permitting weaning of TPN. Alternatively, when there is no hope for adaptation, these infants are maintained on TPN in hopes that they will grow to a size and state of general health satisfactory for either isolated intestinal transplant when liver function is preserved or combined liver-intestinal transplantation when the liver is irreparably damaged. Thus, it is imperative to provide enough parenteral nutrition to facilitate growth while minimizing TPN constituents predisposing to liver damage. Liver disease associated with intestinal failure (IFALD) seems to occur due to a variety of host factors combined with deleterious components of TPN. Host factors include an immature bile secretory mechanism, bile stasis due to fasting, and repeated septic episodes resulting in endotoxemia. Many constituents of TPN are associated with liver damage. Excessive glucose may result in fatty liver and/or hepatic fibrosis, excessive protein may lead to reduced bile flow, and phytosterols present in intravenous lipid may produce direct oxidant damage to the liver or may impede cholesterol synthesis and subsequent bile acid synthesis. Parenteral strategies employed to minimize TPN damage include reducing glucose infusion rates, reducing parenteral protein load, and reducing parenteral lipid load. Furthermore, preliminary studies suggest that fish oil-based lipid solutions may have a salutary effect on IFALD. Ultimately, provision of enteral nutrition is imperative for preventing or reversing IFALD as well as facilitating bowel adaptation. While studies of trophic hormones are ongoing, the most reliable current method to facilitate adaptation is to provide enteral nutrition. Continuous enteral feeding remains the mainstay of enteral nutrition support.