New frontiers in the biology of GLP-2

Maternal fructose intake aggravates the harmful effects of a Western diet in rat male descendants impacting their cholesterol metabolism

Scope: fructose consumption from added sugars correlates with the epidemic rise in MetS and CVD. Maternal fructose intake has been described to program metabolic diseases in progeny. However, consumption of fructose-containing beverages is allowed during gestation. Cholesterol is also a well-known risk factor for CVD. Therefore, it is essential to study Western diets which combine fructose and cholesterol and how maternal fructose can influence the response of progeny to these diets. Methods and results: a high-cholesterol (2%) diet combined with liquid fructose (10%), as a model of an unhealthy Western diet, was administered to descendants from control and fructose-fed mothers. Gene (mRNA and protein) expression and plasma, fecal and tissue parameters of cholesterol metabolism were measured. Interestingly, progeny from fructose-fed dams consumed less liquid fructose and cholesterol-rich chow than males from control mothers. Moreover, descendants of fructose-fed mothers fed a Western diet showed an increased cholesterol elimination through bile and feces than males from control mothers. Despite these mitigating circumstances to develop a proatherogenic profile, the same degree of hypercholesterolemia and severity of steatosis were observed in all descendants fed a Western diet, independently of maternal intake. An increased intestinal absorption of cholesterol, synthesis, esterification, and assembly into lipoprotein found in males from fructose-fed dams consuming a Western diet could be the cause. Moreover, an augmented GLP2 signalling seen in these animals would explain this enhanced lipid absorption. Conclusions: maternal fructose intake, through a fetal programming, makes a Western diet considerably more harmful in their descendants than in the offspring from control mothers.

Inflammation and epithelial repair predict mortality, hospital readmission, and growth recovery in complicated severe acute malnutrition

Severe acute malnutrition (SAM) is the most high-risk form of undernutrition, particularly when children require hospitalization for complications. Complicated SAM is a multisystem disease with high inpatient and postdischarge mortality, especially in children with comorbidities such as HIV; however, the underlying pathogenesis of complicated SAM is poorly understood. Targeted multiplex biomarker analysis in children hospitalized with SAM (n = 264) was conducted on plasma samples, and inflammatory markers were assessed on stool samples taken at recruitment, discharge, and 12 to 24 and 48 weeks after discharge from three hospitals in Zimbabwe and Zambia. Compared with adequately nourished controls (n = 173), we found that at baseline, complicated SAM was characterized by systemic, endothelial, and intestinal inflammation, which was exacerbated by HIV infection. This persisted over 48 weeks despite nutritional recovery and was associated with children's outcomes. Baseline plasma concentrations of vascular endothelial growth factor, glucagon-like peptide-2, and intestinal fatty acid-binding protein were independently associated with lower mortality or hospital readmission over the following 48 weeks. Following principal components analysis of baseline biomarkers, higher scores of a component representing growth factors was associated with greater weight-for-height z score recovery and lower mortality or hospital readmission over the 48 weeks. Conversely, components representing higher gut and systemic inflammation were associated with higher mortality or hospital readmission. These findings highlight the interplay between inflammation, which damages tissues, and growth factors, which mediate endothelial and epithelial regeneration, and support further studies investigating interventions to reduce inflammation and promote epithelial repair as an approach to reducing mortality and improving nutritional recovery.

Effect of kraft pulp inclusion in calf starter on performance, health, and plasma concentration of glucagon-like peptide 2 in calves

Kraft pulp (KP), an intermediate product obtained when wood chips are converted to paper, contains highly digestible fiber. This study evaluated the effect of KP inclusion in calf starters on growth performance, health, and plasma glucagon-like peptide 2 (GLP-2) concentration in calves. Twenty-five Holstein heifer calves were raised on a high plane of nutrition program using milk replacer containing 29% crude protein and 18% fat until 49 d after birth, and were fed calf starters containing KP at 0 (CON; n = 14) or 12% (KPS; n = 11) on a dry matter basis. All calves were fed the treatment calf starters and timothy hay ad libitum. Blood was collected at 4, 14, 21, 35, 49, 70, and 91 d after birth. Dry matter intake (DMI) of milk replacer and hay was not affected by treatment, whereas calf starter DMI was lower for KPS (0.93 kg/d) than for CON (1.03 kg/d). Higher neutral detergent fiber (NDF) content in KPS (31.7%) than in the CON starter (22.1%) resulted in higher NDF intake for KPS (0.55 kg/d) than for CON (0.47 kg/d). However, the consumption of starch was lower for KPS (0.29 kg/d) than for CON (0.33 kg/d). Despite the lower starter intake for KPS, body weight and average daily gain did not differ between treatments. No significant difference was observed in the plasma concentrations of metabolites, except for β-hydroxybutyrate (BHB); BHB concentration was lower for KPS (216 μmol/L) than for CON (257 μmol/L). The area under the curve for plasma GLP-2 concentration was higher for KPS (54.1 ng/mL × d) than for CON (36.0 ng/mL × d). Additionally, the fecal score postweaning (1.19 and 1.48 for KPS and CON, respectively) and the number of days that calves developed diarrhea throughout the experimental period (2.50 d and 8.10 d for KPS and CON, respectively) were lower for KPS than for CON. These results indicate that feeding KP reduces the severity and frequency of diarrhea without adversely affecting growth performance. This could be attributed to the increased plasma GLP-2 concentration induced by higher NDF intake.

Proglucagon-Derived Peptides as Therapeutics

Initially discovered as an impurity in insulin preparations, our understanding of the hyperglycaemic hormone glucagon has evolved markedly over subsequent decades. With description of the precursor proglucagon, we now appreciate that glucagon was just the first proglucagon-derived peptide (PGDP) to be characterised. Other bioactive members of the PGDP family include glucagon-like peptides -1 and -2 (GLP-1 and GLP-2), oxyntomodulin (OXM), glicentin and glicentin-related pancreatic peptide (GRPP), with these being produced via tissue-specific processing of proglucagon by the prohormone convertase (PC) enzymes, PC1/3 and PC2. PGDP peptides exert unique physiological effects that influence metabolism and energy regulation, which has witnessed several of them exploited in the form of long-acting, enzymatically resistant analogues for treatment of various pathologies. As such, intramuscular glucagon is well established in rescue of hypoglycaemia, while GLP-2 analogues are indicated in the management of short bowel syndrome. Furthermore, since approval of the first GLP-1 mimetic for the management of Type 2 diabetes mellitus (T2DM) in 2005, GLP-1 therapeutics have become a mainstay of T2DM management due to multifaceted and sustainable improvements in glycaemia, appetite control and weight loss. More recently, longer-acting PGDP therapeutics have been developed, while newfound benefits on cardioprotection, bone health, renal and liver function and cognition have been uncovered. In the present article, we discuss the physiology of PGDP peptides and their therapeutic applications, with a focus on successful design of analogues including dual and triple PGDP receptor agonists currently in clinical development.

Dietary carbohydrate effects on histological features of ileal mucosa in White Leghorn chicken

White Leghorn chickens were divided into the control, low-carbohydrate (CHO), and CHO-free groups to investigate dietary CHO’s significance on histological features of chicken ileal mucosa. Paraffin sections of distal ileum from each chicken were stained by periodic acid-Schiff reaction and subjected to morphometrical analysis. Most villi in the control group had a fingerlike shape but those of the experimental groups showed irregular shapes. Villus height, crypt depth and the number of mitotic cells per crypt were significantly lower in the CHO-free group than in the control group. The density of goblet cells also showed a significant decreasing trend with a reduction in dietary CHO level. In conclusion, dietary CHO positively affects the proliferation of epithelial cells in the chicken ileum.

Role of Proglucagon Peptides in Osmoregulation

Glucagon-like peptide-1 (GLP-1), a product of partial proteolysis of proglucagon, is involved not only in regulation of carbohydrates, but also in water-salt metabolism. The study examined the role of proglucagon derivatives GLP-1, GLP-2, and oxyntomodulin in rat osmoregulation. Of them, only blood plasma GLP-1 increased in response to water load (20 ml/kg). Administration of glucose (1.5 g/kg) elevated GLP-1 and oxyntomodulin but did not change the level of GLP-2. GLP-1 accelerated excretion of excess water during hyperhydration, whereas GLP-2 decreased this parameter. No physiological effects of oxyntomodulin in the kidneys were revealed. Probably, the blood levels of proglucagon derivatives are independently regulated for each peptide. In contrast to GLP-2 and oxyntomodulin, GLP-1 is involved in osmoregulation.

Glucagon-like Peptide 2 Concentrations Vary in Zambian Children During Diarrhoea, in Malnutrition and Seasonally

OBJECTIVES

Glucagon-like peptide 2 (GLP-2) is a 33 amino acid peptide hormone released from enteroendocrine L-cells following nutrient ingestion. It has been shown to exert trophic effects on the gut. We set out to measure GLP-2 concentrations in blood in children with diarrhoea and malnutrition.

METHODS

GLP-2 levels were measured in blood samples collected from 5 different groups of children (n = 324) at different time points: those with acute diarrhoea, during illness and 3 weeks after recovery; persistent diarrhoea and severe acute malnutrition; controls contemporaneous for diarrhoea; stunted children from the community; and controls contemporaneous for the stunted children. Stool biomarkers and pathogen analysis were carried out on the children with stunting.

RESULTS

GLP-2 concentrations were higher during acute diarrhoea (median 3.1 ng/mL, interquartile range 2.1, 4.4) than on recovery (median 1.8, interquartile range 1.4, 3.1; P = 0.001), but were not elevated in children with persistent diarrhoea and severe acute malnutrition. In stunted children, there was a progressive decline in GLP-2 levels from 3.2 ng/mL (1.9, 4.9) to 1.0 (0.0, 2.0; P < 0.001) as the children became more stunted. Measures of seasonality (rainfall, temperature,Food Price Index, and Shiga toxin-producing Escherichia coli) were found to be significantly associated with GLP-2 concentrations in multivariable analysis. We also found a correlation between stool inflammatory biomarkers and GLP-2.

CONCLUSIONS

In diarrhoea, GLP-2 levels increased in acute but not persistent diarrhoea. Malnutrition was associated with reduced concentrations. GLP-2 displayed seasonal variation consistent with variations in nutrient availability.

The effect of tributyrin supplementation to milk replacer on plasma glucagon-like peptide 2 concentrations in pre-weaning calves

The objective of this study was to evaluate the effect of tributyrin (TB) supplementation to milk replacer (MR) on performance, health, and blood concentrations of metabolite and glucagon-like peptide (GLP-2) in pre-weaning calves. Twenty Holstein heifer calves were raised on an intensified nursing program using MR supplemented with either palm oil (CON) or TB (TB) at 0.3% (as fed basis) for 7 weeks starting 1 week after birth. Calves were fed a calf starter and kleingrass from the beginning of the study. Blood samples were obtained weekly to measure blood glucose, serum β-hydroxybutyric acid (BHBA), insulin-like growth factor 1 (IGF-1), and plasma GLP-2 concentrations. Starter DMI and metabolizable energy (ME) intake were lower in TB calves at 46, 47, from 49 to 55 days after birth compared with the CON calves. However, any growth parameters were not affected by TB treatment. Blood glucose, serum BHBA, and IGF-1 concentrations were not affected by TB supplementation. On the other hand, mean plasma GLP-2 concentration among whole experimental period was higher for TB (0.60 ng/ml) compared with CON (0.41 ng/ml). In conclusion, feeding MR supplemented with TB increases plasma GLP-2 concentration, which might counterbalance the growth performance of TB calves despite the decreased ME intake.

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.

COMPARATIVE GUT PHYSIOLOGY SYMPOSIUM: Comparative physiology of glucagon-like peptide-2: Implications and applications for production and health of ruminants

Glucagon-like peptide-2 (GLP-2) is a 33-amino acid peptide derived from proteolytic cleavage of proglucagon by prohormone convertase 1/3 in enteroendocrine L cells. Studies conducted in humans, in rodent models, and in vitro indicate that GLP-2 is secreted in response to the presence of molecules in the intestinal lumen, including fatty acids, carbohydrates, amino acids, and bile acids, which are detected by luminal chemosensors. The physiological actions of GLP-2 are mediated by its G protein-coupled receptor expressed primarily in the intestinal tract on enteric neurons, enteroendocrine cells, and myofibroblasts. The biological activity of GLP-2 is further regulated by dipeptidyl peptidase IV, which rapidly cleaves the N-terminus of GLP-2 that is responsible for GLP-2 receptor activation. Within the gut, GLP-2 increases nutrient absorption, crypt cell proliferation, and mesenteric blood flow and decreases gut permeability and motility, epithelial cell apoptosis, and inflammation. Outside the gut, GLP-2 reduces bone resorption, can suppress appetite, and is cytoprotective in the lung. Thus, GLP-2 has been studied intensively as a therapeutic to improve intestinal function of humans during parenteral nutrition and following small bowel resection and, more recently, as a treatment for osteoporosis and obesity-related disorders and to reduce cellular damage associated with inflammation of the gut and lungs. Recent studies demonstrate that many biological actions and properties of GLP-2 in ruminants are similar to those in nonruminants, including the potential to reduce intestinal nitro-oxidative stress in calves caused by parasitic diseases such as coccidiosis. Because of its beneficial impacts on nutrient absorption, gut healing, and normal gut development, GLP-2 therapy offers significant opportunities to improve calf health and production efficiency. However, GLP-2 therapies require an extended time course to achieve desired physiological responses, as well as daily administration because of the hormone's short half-life. Thus, practical means of administration and alternative strategies to enhance basal GLP-2 secretion (e.g., through specific feed additives), which are more likely to achieve consumer acceptance, are needed. Opportunities to address these challenges are discussed.

Postprandial effects on plasma lipids and satiety hormones from intake of liposomes made from fractionated oat oil: two randomized crossover studies

Background

The composition and surface structure of dietary lipids influence their intestinal degradation. Intake of liposomes made of fractionated oat oil (LOO) is suggested to affect the digestion process and postprandial lipemia and also induce satiety.

Objective

In the present study, the metabolic effects on plasma lipids and gut hormones related to satiety were investigated in healthy individuals after intake of LOO, with dairy lipids as placebo.

Design

Two blinded randomized studies with crossover design were performed. In the first study, 19 subjects consumed 35 g lipids from LOO or yoghurt in a breakfast meal. In a follow-up study, 15 women consumed 14 or 1.8 g lipids from LOO mixed in yoghurt. Blood samples were analyzed for plasma lipids, insulin, glucose, and intestinal hormones CCK, PYY, GLP-1, and GLP-2 before and four times after the meal. Subjective analysis of satiety was measured using a visual analog scale questionnaire. Participants recorded their food intake during the rest of the day.

Results

Intake of 35 and 14 g lipids from LOO significantly increased plasma concentrations of CCK, GLP-1, GLP-2, and PYY postprandially. This coincided with a prolonged elevation of triglycerides and large cholesterol-containing particles. Non-esterified fatty acids decreased after intake of 14 and 1.8 g lipids from LOO. The subjective sensation of satiety in women was increased 7 h after intake of 35 g lipids from LOO without any difference in food intake. Our results indicate that intake of 14 g lipids from LOO at breakfast substantially reduced energy intake during the rest of the day.

Conclusions

This study suggests that intake of LOO prolong lipid digestion, affect postprandial plasma lipids and have an effect on satiety. The effect of LOO on GLP-2 indicates that intake of LOO also improve gut health.

Distribution of glucagon-like peptide (GLP)-2-immunoreactive cells in the chicken small intestine: antigen retrieval immunohistochemistry

An antigen retrieval method for immunohistochemical staining of glucagon-like peptide (GLP)-2-immunoreactive cells was investigated in the chicken small intestine. GLP-2-immunoreactive cells were observed as open-typed endocrine cells in the villous epithelium and crypts on both antigen retrieval agent-treated and untreated preparations. No obvious differences were detected in morphological features of GLP-2-immunoreactive cells between treated and untreated preparations. The frequencies of occurrence of GLP-2-immunoreactive cells, however, were significantly different in treated and untreated preparations: in the proximal and distal regions of jejunum and ileum obtained from untreated preparations, the frequencies of occurrence were 0.5 ± 0.2, 0.7 ± 0.1, 0.9 ± 0.2 and 1.5 ± 0.3, respectively (cell numbers per mucosal area: cells/mm², mean ± SD), whereas those from treated sections were 14.7 ± 2.3, 19.8 ± 2.3, 23.5 ± 4.7 and 34.6 ± 4.9 cells/mm², respectively. These data indicate that this antigen retrieval method is able to make immunoreactive GLP-2 available for detection and that GLP-2 may act as one of the common hormones secreted by L cells in the chicken small intestine.

Digestive physiology of the pig symposium: potential applications of knowledge of gut chemosensing in pig production

Pig production is a commodity business, which makes it a cost-driven business. Pig producers and their advisors are appropriately reluctant to adopt technologies without confidence that improved production will more than pay for the cost of the technology. Physiological effects of technologies targeting gut sensory pathways must translate to demonstrably improved health and/or productive performance if they are to be adopted. The types and degrees of stressors experienced by pigs in commercial production vary widely and often differ from those in research herds, and those variations influence their productive responses to nutritional and health technologies. Pigs are most vulnerable to disease soon after weaning, and the diets fed to pigs at that time are more expensive and offered in much smaller amounts than those fed later in life. Those factors make it easier to justify expensive dietary technologies for young pigs than for older ones. New developments in gut chemosensing appear important, but their practical application is not yet clear. We suggest investigation of the potential to connect chemical detection by the gut to pig productivity and/or efficiency through these mechanisms: 1) trophic effects on the intestines, which lead to improved enteric health or enhanced nutrient digestion and absorption, 2) enhanced barrier function in the intestinal mucosa, 3) increased feed intake, 4) enhanced insulin secretion and sensitivity, which may be especially useful in lactating sows to improve subsequent reproduction, and 5) other signals triggered by products of enteric fermentation, possibly short-chain fatty acids, that may influence gut integrity, feed intake, and reproductive function. Each of these mechanisms relates to a practical issue in pig production. Practical application would likely be achieved through dietary changes, but separate management factors, drugs, or other interventions may also be developed.

Gene expression in intestinal mucosal biopsy specimens obtained from dogs with chronic enteropathy

OBJECTIVE

To characterize mucosal gene expression in dogs with chronic enteropathy (CE).

ANIMALS

18 dogs with CE and 6 healthy control dogs.

PROCEDURES

Small intestinal mucosal biopsy specimens were endoscopically obtained from dogs. Disease severity in dogs with CE was determined via inflammatory bowel index scores and histologic grading of biopsy specimens. Total RNA was extracted from biopsy specimens and microchip array analysis (approx 43,000 probe sets) and quantitative reverse transcriptase PCR assays were performed.

RESULTS

1,875 genes were differentially expressed between dogs with CE and healthy control dogs; 1,582 (85%) genes were downregulated in dogs with CE, including neurotensin, fatty acid-binding protein 6, fatty acid synthase, aldehyde dehydrogenase 1 family member B1, metallothionein, and claudin 8, whereas few genes were upregulated in dogs with CE, including genes encoding products involved in extracellular matrix degradation (matrix metallopeptidases 1, 3, and 13), inflammation (tumor necrosis factor, interleukin-8, peroxisome proliferator-activated receptor γ, and S100 calcium-binding protein G), iron transport (solute carrier family 40 member 1), and immunity (CD96 and carcinoembryonic antigen-related cell adhesion molecule [CEACAM] 18). Dogs with CE and protein-losing enteropathy had the greatest number of differentially expressed genes. Results of quantitative reverse transcriptase PCR assay for select genes were similar to those for microchip array analysis.

CONCLUSIONS AND CLINICAL RELEVANCE

Expression of genes encoding products regulating mucosal inflammation was altered in dogs with CE and varied with disease severity. Impact for Human Medicine-Molecular pathogenesis of CE in dogs may be similar to that in humans with inflammatory bowel disease.

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.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

DISCUSSION

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

Enteroendocrine cells: neglected players in gastrointestinal disorders?

Enteroendocrine cells (EEC) form the basis of the largest endocrine system in the body. They secrete multiple regulatory molecules which control physiological and homeostatic functions, particularly postprandial secretion and motility. Their key purpose is to act as sensors of luminal contents, either in a classical endocrine fashion, or by a paracrine effect on proximate cells, notably vagal afferent fibres. They also play a pivotal role in the control of food intake, and emerging data add roles in mucosal immunity and repair. We propose that EEC are fundamental in several gastrointestinal pathologies, notably Post-infectious Irritable Bowel Syndrome, infectious enteritis, and possibly inflammatory bowel disease. Further work is needed to fully illustrate the importance, detailed biology and therapeutic potential of these frequently overlooked cells.

Peptides from Lactobacillus hydrolysates of bovine milk caseins inhibit prolyl-peptidases of human colon cells

Prolyl-rich peptides derived from hydrolysates of bovine caseins have been previously shown to inhibit angiotensin converting enzyme (ACE) activity, suggesting that they may also be able to inhibit the enzymatic activities of prolyl-specific peptidases. This study shows that peptides derived from α(S1)-casein and β-casein inhibited the enzymatic activities of purified recombinant matrix metalloprotease (MMP)-2, MMP-7, and MMP-9. The inhibitory efficacy was sequence-dependent. These peptides also selectively inhibited the enzymatic activities of prolyl-amino-peptidases, prolyl-amino-dipeptidases, and prolyl-endopeptidases in extracts of HT-29 and SW480 human colon carcinoma cells, but not in intact cells. They were not cytotoxic or growth inhibitory for these cells. Thus, the prolyl-rich selected peptides were good and selective inhibitors of MMPs and post-proline-cleaving proteases, demonstrating their potential to control inadequate proteolytic activity in the human digestive tract, without inducing cytotoxic effects.

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

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

Synthesis and structure-activity relationships of potent 1-(2-substituted-aminoacetyl)-4-fluoro-2-cyanopyrrolidine dipeptidyl peptidase IV inhibitors

Dipeptidyl peptidase IV (DPP-IV) inhibitors have attracted attention as potential drugs for use in the treatment of type 2 diabetes because they prevent the degradation of glucagon-like peptide-1 (GLP-1) and extend its duration of action. We previously reported that 2-cyano-4-fluoropyrrolidines act as potent DPP-IV inhibitors and have been modifying the 1-position of pyrrolidine to obtain more useful inhibitors. An L-tert-butylglycine derivative was found to be a stable and potent DPP-IV inhibitor that exhibits a glucose lowering effect in vivo. Here, we report the synthesis of and biological data on the aforementioned derivatives.

Appetite signaling: from gut peptides and enteric nerves to brain

The signaling systems underlying eating behavior control are complex. The current review focuses on gastrointestinal (GI) signaling systems as physiological key functions for metabolic control. Many of the peptides that are involved in the regulation of food intake in the brain are also found in the enteric nervous system and enteroendocrine cells of the mucosa of the GI tract. The only identified hunger-driving signal from the GI tract is ghrelin, which is mainly found in the mucosa of the stomach. Neuropeptides in the brain that influence food intake, of which neuropeptide Y, agouti gene-related peptide and orexins are stimulatory, while melanocortins and alpha-melanocortin stimulating hormone are inhibitory, are influenced by peptide signaling from the gut. These effects may take place directly through action of gut peptide in the brain or through nervous signaling from the periphery to the brain. The criteria for considering a gut hormone or neurotransmitter in a satiety signal seem to be fulfilled for cholecystokinin, glucagon-like peptide-1 and peptide YY(3-36). Other endogenous gut signals do not fulfill these criteria as they do not increase food intake in knock-out animals or in response to receptor antagonism, or display an inconsistent temporal profile with satiety and termination of the meal. Satiety signals from the GI tract act through the arcuate nucleus of the hypothalamus and the solitary tract nucleus of the brain stem, where neuronal networks directly linked to hypothalamic centers for food intake and eating behavior are activated. We have primarily focused on GI effects of various gut peptides involved in the regulation of food intake, using motor activity as a biomarker for the understanding of gut peptide effects promoting satiety.

Effect of glucagon-like peptide-1 and -2 on regulation of food intake, body temperature and locomotor activity in the Japanese quail

To investigate the physiological roles of glucagon-like peptide-1 (GLP-1) and glucagon-like peptide-2 (GLP-2) in avian species, we elucidated the effect of intraperitoneal (i.p.) and intracerebroventricular (i.c.v.) administration of GLP-1 and GLP-2 on food intake, body temperature and gross locomotor activity in adult Japanese quail. Both i.p. and i.c.v. administration of GLP-1 suppressed food intake at 2, 4 and 12h after administration. Moreover, both i.p. and i.c.v. administration of GLP-1 significantly decreased both body temperature and gross locomotor activity 2h after administration. On the other hand, both i.p. and i.c.v. administration of GLP-2 had no effect on food intake, body temperature or gross locomotor activity. These results suggest that GLP-1 may have an important role in the regulation of food intake, body temperature and locomotor activity while GLP-2 may have no apparent effect on feeding regulation in adult Japanese quail.

Gut hormones, and short bowel syndrome: The enigmatic role of glucagon-like peptide-2 in the regulation of intestinal adaptation

Short bowel syndrome (SBS) refers to the malabsorption of nutrients, water, and essential vitamins as a result of disease or surgical removal of parts of the small intestine. The most common reasons for removing part of the small intestine are due to surgical intervention for the treatment of either Crohn's disease or necrotizing enterocolitis. Intestinal adaptation following resection may take weeks to months to be achieved, thus nutritional support requires a variety of therapeutic measures, which include parenteral nutrition. Improper nutrition management can leave the SBS patient malnourished and/or dehydrated, which can be life threatening. The development of therapeutic strategies that reduce both the complications and medical costs associated with SBS/long-term parenteral nutrition while enhancing the intestinal adaptive response would be valuable.

Currently, therapeutic options available for the treatment of SBS are limited. There are many potential stimulators of intestinal adaptation including peptide hormones, growth factors, and neuronally-derived components. Glucagon-like peptide-2 (GLP-2) is one potential treatment for gastrointestinal disorders associated with insufficient mucosal function. A significant body of evidence demonstrates that GLP-2 is a trophic hormone that plays an important role in controlling intestinal adaptation. Recent data from clinical trials demonstrate that GLP-2 is safe, well-tolerated, and promotes intestinal growth in SBS patients. However, the mechanism of action and the localization of the glucagon-like peptide-2 receptor (GLP-2R) remains an enigma. This review summarizes the role of a number of mucosal-derived factors that might be involved with intestinal adaptation processes; however, this discussion primarily examines the physiology, mechanism of action, and utility of GLP-2 in the regulation of intestinal mucosal growth.

Identification and characterization of surrogate peptide ligand for orphan G protein-coupled receptor mas using phage-displayed peptide library

In the present study, a phage-displayed random peptide library was used to identify surrogate peptide ligands for orphan GPCR mas. Sequence analysis of the isolated phage clones indicated a selective enrichment of some peptide sequences. Moreover, multiple alignments of the isolated phage clones gave two conserved peptide motifs from which we synthesized peptide MBP7 for further evaluation. Characterization of the representative phage clones and the synthetic peptide MBP7 by immunocytochemistry revealed a strong punctate cell surface staining in CHO cells expressing mas-GFP fusion protein. The isolated phage clones and synthetic peptide MBP7 induced mas internalization in a stable CHO cell clone (MC0M80) over-expressing mas. In addition, MBP7-stimulated phospholipase C activity and intracellular calcium mobilization in these same cells. In summary, we have demonstrated a systematic approach to derive surrogate peptide ligands for orphan GPCRs. With this technique, we have identified two conserved peptide motifs which allow us to identify potential protein partners for mas, and have generated a peptide agonist MBP7 which will be invaluable for functional characterization of the mas oncogene.

Synthesis and structure–activity relationships of potent 3- or 4-substituted-2-cyanopyrrolidine dipeptidyl peptidase IV inhibitors

Dipeptidyl peptidase IV (DPP-IV) inhibitors have attracted attention as potential drugs for use in the treatment of type 2 diabetes because they prevent degradation of glucagon-like peptide-1 (GLP-1) and extend its duration of action. A series of 2-cyanopyrrolidines are among the most potent of DPP-IV inhibitors. We focused our attention on substitutions at the 3- or 4-position of 2-cyanopyrrolidines and synthesized and evaluated various derivatives. Among them, the 4-fluoro derivative was found to exhibit better DPP-IV inhibitory activity and higher plasma drug concentrations after oral administration to rats than the 4-unsubstituted derivative. We report here on the synthesis and biological data of the aforementioned derivatives.

Enteroendocrine cells and 5-HT availability are altered in mucosa of guinea pigs with TNBS ileitis

Enteroendocrine cells act as sensory transducers, releasing 5-HT and numerous peptides that are involved in regulating motility, secretion, and gut sensation. The action of mucosal 5-HT is terminated by a 5-HT reuptake transporter (SERT). In this study, we examined the hypothesis that ileitis leads to changes in enteroendocrine cell populations and mucosal 5-HT availability. Ileitis was induced in guinea pigs by intraluminal injection of 2,4,6-trinitrobenzenesulfonic acid and experiments were conducted 3, 7, and 14 days after treatment. The number of somatostatin, neurotensin, and 5-HT-immunoreactive cells increased at 3 and 7 days of ileitis, respectively, whereas no significant changes in the numbers of cholecystokinin, glucagon-like peptide-2, glucose-dependent insulinotropic peptide, and peptide YY-immunoreactive cells were observed. Chemical stimulation of the inflamed mucosa with sodium deoxycholic acid significantly increased 5-HT release compared with basal release. Mechanical stimulation of the mucosa potentiated the effect of the chemical stimuli at day 7. Epithelial SERT immunoreactivity was significantly reduced during the time course of inflammation. Thus changes in enteroendocrine cell populations and 5-HT availability could contribute to the altered motility and secretion associated with intestinal inflammation by disrupting mucosal signaling to enteric nerves involved in peristaltic and secretory reflexes.

Peripheral and central signals in the control of eating in normal, obese and binge-eating human subjects

The worldwide increase in the incidence of obesity is a consequence of a positive energy balance, with energy intake exceeding expenditure. The signalling systems that underlie appetite control are complex, and the present review highlights our current understanding of key components of these systems. The pattern of eating in obesity ranges from over-eating associated with binge-eating disorder to the absence of binge-eating. The present review also examines evidence of defects in signalling that differentiate these sub-types. The signalling network underlying hunger, satiety and metabolic status includes the hormonal signals leptin and insulin from energy stores, and cholecystokinin, glucagon-like peptide-1, ghrelin and peptide YY3-36 from the gastrointestinal tract, as well as neuronal influences via the vagus nerve from the digestive tract. This information is routed to specific nuclei of the hypothalamus and brain stem, such as the arcuate nucleus and the solitary tract nucleus respectively, which in turn activate distinct neuronal networks. Of the numerous neuropeptides in the brain, neuropeptide Y, agouti gene-related peptide and orexin stimulate appetite, while melanocortins and alpha-melanocortin-stimulating hormone are involved in satiety. Of the many gastrointestinal peptides, ghrelin is the only appetite-stimulating hormone, whereas cholecystokinin, glucagon-like peptide-1 and peptide YY3-36 promote satiety. Adipose tissue provides signals about energy storage levels to the brain through leptin, adiponectin and resistin. Binge-eating has been related to a dysfunction in the ghrelin signalling system. Moreover, changes in gastric capacity are observed, and as gastric capacity is increased, so satiety signals arising from gastric and post-gastric cues are reduced. Understanding the host of neuropeptides and peptide hormones through which hunger and satiety operate should lead to novel therapeutic approaches for obesity; potential therapeutic strategies are highlighted.

Glucagon-like peptide-2 inhibits antral emptying in man, but is not as potent as glucagon-like peptide-1

BACKGROUND

GLP-1 (glucagon-like peptide-1) and GLP-2 (glucagon-like peptide-2) are released in equimolar amounts in response to meal ingestion. GLP-1 inhibits gastric emptying and reduces postprandial gastric and exocrine pancreatic secretion and may play a physiological regulatory role in controlling appetite and energy intake in humans. The role of GLP-2 is more uncertain. Based on the results of animal studies, it has been suggested that GLP-2 may induce intestinal epithelial growth and inhibit gastric motility. The aim of this study was to determine to what extent GLP-2 alone or together with GLP-1 inhibits gastric emptying and the sensation of hunger in man.

METHODS

Eight healthy volunteers were tested in a double-blind, placebo-controlled fashion. Antral emptying of a liquid meal and hunger ratings were determined using ultrasound technology and visual analogue scales scoring during infusions of saline, GLP-2 (0.5, and 1.0 pmol kg body wt(-1) min(-1)), GLP-1 (0.5 pmol kg body wt(-1) min(-1)) or GLP-1 and GLP-2 (0.5 pmol kg body wt(-1) min(-1)).

RESULTS

The GLP-2 infusions resulted in a dose-dependent increase in antral emptying time (35%; ns and 75%; P = 0.049) compared to saline, but GLP-2 was less potent than GLP-1, which increased the antral emptying time by 192% (P < 0.001). Addition of GLP-2 to the GLP-1 infusion did not alter the antral emptying time compared with GLP-1 alone. The GLP-1 infusion decreased the sensation of hunger compared with saline (P = 0.023), whereas the two GLP-2 infusions had no significant effect. Addition of GLP-2 to the GLP-1 infusion did not decrease the sensation of hunger further.

CONCLUSIONS

Both GLP-1 and GLP-2 inhibit antral emptying in man, but GLP-1 is more potent.

Dipeptidyl peptidase IV activity and/or structure homologues (DASH) and their substrates in cancer

Post-translational modification of proteins is an important regulatory event. Numerous biologically active peptides that play an essential role in cancerogenesis contain an evolutionary conserved proline residue as a proteolytic-processing regulatory element. Proline-specific proteases could therefore be viewed as important "check-points". Limited proteolysis of such peptides may lead to quantitative but, importantly, due to the change of receptor preference, also qualitative changes of their signaling potential. Dipeptidyl peptidase-IV (DPP-IV, EC 3.4.14.5, identical with CD26) was for many years believed to be a unique cell membrane protease cleaving X-Pro dipeptides from the N-terminal end of peptides and proteins. Subsequently, a number of other molecules were discovered, exhibiting various degree of structural homology and DPP-IV-like enzyme activity, capable of cleaving similar set of substrates. These comprise for example, seprase, fibroblast activation protein alpha, DPP6, DPP8, DPP9, attractin, N-acetylated-alpha-linked-acidic dipeptidases I, II and L, quiescent cell proline dipeptidase, thymus-specific serine protease and DPP IV-beta. It is tempting to speculate their potential participation on DPP-IV biological function(s). Disrupted expression and enzymatic activity of "DPP-IV activity and/or structure homologues" (DASH) might corrupt the message carried by their substrates, promoting abnormal cell behavior. Consequently, modulation of particular enzyme activity using e.g. DASH inhibitors, specific antibodies or DASH expression modification may be an attractive therapeutic concept in cancer treatment. This review summarizes recent information on the interactions between DASH members and their substrates with respect to their possible role in cancer biology.

Role of gastrointestinal hormones in postprandial reduction of bone resorption

Collagen type I fragments, reflecting bone resorption, and release of gut hormones were investigated after a meal. Investigations led to a dose escalation study with glucagon like peptide-2 (GLP-2) in postmenopausal women. We found a dose-dependent effect of GLP-2 on the reduction of bone resorption.

INTRODUCTION

The C-terminal telopeptide region of type I collagen as measured in serum (s-CTX) can be used to assess bone resorption. This marker of bone resorption has a significant circadian variation that is influenced by food intake. However, the mediator of this variation has not been identified.

MATERIALS AND METHODS

We studied the release of the gut hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-2 (GLP-2; a representative of the intestinal proglucagon-derived peptides) after ingestion of glucose, fat, protein, and fructose, as well as their effects after parenteral administration in relation to bone turnover processes in healthy volunteers. Furthermore, we studied the effect on bone turnover of a single subcutaneous injection of GLP-2 in four different dosages (100, 200, 400, or 800 microg GLP-2) or placebo in 60 postmenopausal women (mean age, 61 +/- 5 years).

RESULTS

All macronutrients significantly (p < 0.05) reduced bone resorption as assessed by s-CTX (39-52% from baseline), and only the glucagon-like peptides were secreted in parallel. Parenteral administration of GIP and GLP-1 did not result in a reduction of the s-CTX level, whereas GLP-2 caused a statistically significant and dose-dependent reduction in the s-CTX level from baseline compared with placebo (p < 0.05). Urine DPD/creatinine, a marker of bone resorption, was significantly reduced by 25% from baseline in the 800-microg GLP-2 group (p < 0.01). An area under the curve (AUC(0-8h)) analysis for s-CTX after GLP-2 injection confirmed the dose-dependent decrease (ANOVA, p = 0.05). The s-osteocalcin level was unaffected by the GLP-2 treatment.

CONCLUSION

These studies exclude both GIP and GLP-1 as key mediators for the immediate reduction in bone resorption seen after a meal. The dose-dependent reduction of bone resorption markers found after subcutaneous injection of GLP-2 warrants further investigation into the mechanism and importance of GLP-2 for the bone turnover processes.

Inhibition of dipeptidyl peptidase IV (DPP IV) by 2-(2-amino-1-fluoro-propylidene)-cyclopentanecarbonitrile, a fluoroolefin containing peptidomimetic

Novel, potent inhibitors of dipeptidyl peptidase IV (DPP IV, EC 3.4.14.5, CD26), containing the fluoroolefin peptide isostere psi [CFz.dbnd6;C], have been prepared via the intermediacy of the Peterson fluoroolefination reaction. The nitrile containing inhibitors were found to inhibit dipeptidyl peptidase IV competitively with K(i) values for the l-3 and u-3 inhibitors of 7.69 and 6.03 microM, respectively. In contrast to earlier reported fluoroolefin containing inhibitors, the nitriles underwent no detectable degradation at pH 7.6 under buffered conditions.

Interactions between gastric emptying and satiety, with special reference to glucagon-like peptide-1

The slowing of gastric emptying is an important mechanism for the satiating effect of gut peptide signaling. After food intake, cholecystokinin (CCK), as well as glucagon-like peptide-1 (GLP-1) and glucagon-like peptide-2 (GLP-2), are released from the gastrointestinal tract to mediate satiety. In humans, CCK and the GLP-1 have been found to cause satiety in both normal and obese subjects. This satiating effect may be caused by the peptides circulating as hormones with direct effects in the central nervous system, or indirect effects through signals mediated either via the vagus nerve or by activation of vagal afferent fibers due to slow gastric emptying. These peptides also cause gastric relaxation, considered an additional component in the satiating effect of the peptides. To conclude, after food intake, gut peptides may act in concert as neurohormonal satiety signals acting directly in the brain or indirectly via the vagus nerve, as well as through gastric sensory mechanisms to limit food intake.

The gut and food intake: an update for surgeons

Food intake is the simplest and most obvious measure of gastrointestinal function, yet it rarely receives more than cursory attention from surgeons. In this review we cover recent findings on relationships between gut function and appetite regulation mediated via neuropeptides influenced by afferent and efferent vagal activity. Evidence from the new discipline known as neurogastroenterology elucidates gastric and intestinal signals involved in the elicitation of hunger, satiety, and aversion. Discovery of the adipose-tissue-derived hormone, leptin, has energized the field of metabolism spawning increasing numbers of publications related to interactions between leptin and insulin release and glucose disposal, as well as appetitive behavior. Peptides such as cholecystokinin (CCK), the proglucagon-derived peptides, glucagon-like peptides 1 and 2 (GLP-1 and GLP-2), and the recently identified powerful intake-stimulating molecule, orexin, are examples of potential targets for drug development and studies of surgical pathophysiology. A major conclusion of this work is that the considerable redundancy and overlap between mediators of caloric intake subserving survival of the species, while beneficial after foregut surgery, contribute to the complexity of treating the global epidemic of obesity. Possibly knowledge derived from basic research in neurogastroenterology can translate into advances in surgical treatment of obesity.

Therapeutic potential of the intestinotropic hormone, glucagon-like peptide-2

Glucagon-like peptide-2 (GLP-2) is a newly discovered growth factor that has been demonstrated to enhance intestinal growth and function in normal rodents and to prevent damage and facilitate intestinal repair in various animal models of intestinal insufficiency. A recent study has demonstrated that GLP-2 also acts as an intestinotropin in humans with short-bowel syndrome. The high degree of specificity of GLP-2 for induction of intestinal growth, without affecting growth of other peripheral tissues, is determined by the highly localized expression of the GLP-2 receptor in the intestinal epithelium. In this article, we review the regulation of GLP-2 in physiology, from synthesis to metabolism, with a particular emphasis on potential targets in this pathway for therapeutic manipulation of GLP-2 actions. We also discuss the various animal models of intestinal insufficiency that have been used to demonstrate the therapeutic potential of this intestinotropic hormone, including short bowel, intestinal atrophy, enteritis and colitis. The results of these studies indicate that GLP-2 is a promising therapeutic agent for the treatment of various forms of intestinal insufficiency in humans.

Glucagon-like peptide 2: a nutrient-responsive gut growth factor

Glucagon-like peptide 2 (GLP-2) is a 33-amino acid peptide derived from the tissue-specific, post-translational processing of the proglucagon gene expressed in the intestinal enteroendocrine L-cell. The primary stimulus for GLP-2 secretion is nutrient intake, and involves direct luminal stimulation of the L-cell as well as indirect enteroendocrine and neural mechanisms. The biological activity of GLP-2 in circulation is regulated by the proteolytic cleavage of the N-terminus by dipeptidylpeptidase IV. Several studies have shown that GLP-2 has specific trophic effects on the small and large intestine, which are mediated by stimulation of cell proliferation and inhibition of apoptosis and proteolysis. GLP-2 also has been shown to suppress gastric motility and acid secretion, increase hexose transport activity and suppress food intake, specifically when infused centrally. The actions of GLP-2 are mediated by a G-protein-linked, membrane receptor (GLP-2R) that is localized largely to the gastrointestinal tract, but also is found in the brain. The secretion of GLP-2 and expression of the GLP-2R are present in the late gestation fetus. However, the developing intestine does not become responsive to the trophic effect of GLP-2 until after birth. Based on its efficacy in preventing atrophy and stimulating growth in the neonatal gut, GLP-2 may be a promising therapeutic adjuvant for treatment of infants with compromised gut function.

Secretion of trophic gut peptides is not different in bolus- and continuously fed piglets

In neonates, bolus feeding is associated with greater rates of intestinal growth than is continuous feeding. We tested whether the concentrations and secretion rates of trophic gut peptides are higher in bolus-fed than in continuously fed piglets. Five 21-d-old piglets were surgically implanted with gastric, arterial and portal catheters and a portal blood flow probe. At postnatal d 30 and 31, pigs received an equal amount of primed continuous or bolus feeding of a cow's milk formula in a randomized, crossover design. During a 6-h period, portal blood flow and arterial and portal concentrations of glucagon-like peptide-2 (GLP-2), peptide YY (PYY) and gastric inhibitory polypeptide (GIP) were measured. All hormone levels were significantly increased within 1 h of the start of the experiment, independent of the feeding modality. There were no differences between bolus and continuous feeding in either the arterial concentrations or secretion rates of GLP-2, PYY and GIP. In both treatment groups, the increases in the plasma concentrations of GLP-2 and GIP after feeding were substantially greater than those for PYY. We conclude that the production or circulating concentrations of GLP-2, PYY and GIP are not significantly different in bolus- and primed continuously fed piglets.