Advances in glucagon like peptide-2 therapy. physiology, current indications and future directions

The treatment paradigm for pediatric patients with short bowel syndrome (SBS) and intestinal failure (IF) has changed significantly over recent years; the development of dedicated IF teams, refinements in PN and surgical treatments have greatly improved survival. The majority of SBS patients undergo intestinal adaptation such that nutrient absorption from enteral feeds increases and the child can come off of PN. This "adaptation" or upregulation in nutrient absorptive capacity is still poorly understood; the enteric hormone Glucagon like peptide 2 (GLP-2) appears to be a key regulator in this process. The development of Teduglutide, a long acting GLP-2 ligand as a therapy to specifically enhance adaptation has been anticipated as a further shift in the paradigm. This article reviews the physiology of GLP-2 with an emphasis on the known or potential roles in infants and children with SBS and IF. The results and implications of the present studies and approved indications for GLP-2 and its ligands are discussed. Finally, the potential future uses of GLP-2 ligands in the pediatric population are considered.

Updating the Surgical Preference List

Surgical procedure ‘preference lists’ are used worldwide, but their practice varies widely. Despite being positioned at a critical point in a surgical care pathway, they are often underemphasized, poorly maintained, and substandard. The following editorial material is gleaned from our experience in the set-up of a tertiary hospital on a green field site in Qatar. We comment on the use of preference lists, and contend that focus on standardizing and maintaining preference lists within an electronic record affords substantial opportunities for cost containment, whilst adding efficiency, safety, and value. We believe this approach represents an ‘easy win’ which would be applicable elsewhere.

The glucagon like peptide-2 'axis': Capacity for production and response following intestinal resection or repair of gastroschisis in infants

PURPOSE

This study investigates the relationship between the enteric hormone glucagon-like peptide 2 (GLP-2) production, sensitivity, and intestinal adaptation in infants following resection or repair of gastroschisis.

METHODS

With IRB approval (UCalgary #10656), consent was obtained from families of infants undergoing surgery for prospective monitoring of nutritional status, GLP-2 levels, and where possible, tissue sampling.

RESULTS

Infants who adapted and weaned from parenteral nutrition (PN) had increased GLP-2 (86±32) n=24 vs. controls: 45±20 n=10 and vs. patients on prolonged PN: 42±6 pM, n=10). This was maintained to one year: weaned patients: 72±49 vs. non-weaned: 35±15 pM (p<0.05). Infants with gastroschisis (n=33) had decreased GLP-2 levels until enteral function was achieved and then became elevated: (21±15 with first feeding vs. 102±60 at full feeds and 60±19 pM at one year). There were no changes in the density or distribution of GLP-2 producing L-cells related to gestational age, nor in the expression of the GLP-2 receptor.

CONCLUSION

GLP-2 levels correlate with intestinal adaptation in infants, and with recovery of intestinal function in gastroschisis. GLP-2 productive capacity (L-cell expression) and GLP-2 receptor expression do not vary with maturity. The findings support a role for GLP-2 in regulating intestinal function. Further study is suggested.

A safety and pharmacokinetic dosing study of glucagon-like peptide 2 in infants with intestinal failure

BACKGROUND & AIMS

Glucagon-like peptide 2 (GLP-2) analogues are approved for adults with intestinal failure (IF), but no studies have included infants. This study examined the pharmacokinetics (PK), safety, and nutritional effects of GLP-2 in infants with IF.

METHODS

With parental consent (Health Canada Protocol:150,979), parenteral nutrition (PN)-dependent infants were treated with 5-20-μg/kg/day GLP-2 for 3days (phase 1), and if tolerated continued for 42days (phase 2). Nutritional therapy was by primary caregivers, and follow-up was to one year.

RESULTS

Six patients were enrolled, age 5.4±3.2months, bowel length: 27±12% of predicted, PN dependent (67±18% of calories). GLP-2 did not affect vital signs, nor were there significant adverse events during the trial. Dosing 5μg/kg/day gave GLP-2 levels of 52-57pmol/L, with no change in half-life or endogenous GLP-2 levels. Enteral feeds, weight, Z scores, stooling frequency, and citrulline levels improved numerically. The trial was discontinued early because of a drop in potency.

CONCLUSIONS

GLP-2 was well tolerated in infants, and pK was similar to children with no changes in endogenous GLP-2 release. The findings suggest that GLP-2 ligands may be safely used in infants and may have beneficial effects on nutritional status. Further study is required.

LEVEL OF EVIDENCE

2b Prospective Interventional Study.

Pathophysiology, prevention, treatment, and outcomes of intestinal failure-associated liver disease

BACKGROUND

Intestinal failure-associated liver disease (IFALD) remains a serious problem in the treatment of infants with nutritional problems and short bowel syndrome.

METHODS

A review of the recent literature from 2010 to 2016, concentrating on articles related to the pathophysiology of IFALD and to outcomes of novel nutritional and pharmacological therapies for neonatal cholestasis in the post-surgical neonate.

RESULTS

The pathophysiology of IFALD relates to an increase sensitivity of the neonatal liver to cholestasis in the non-fed state; prolonged cholestasis almost inevitably results in liver damage which will progress from fibrosis to cirrhosis. Clinically discerned risk factors include premature birth, inflammation, sepsis, disruption of the enterohepatic circulation by creation of a proximal stoma, and the duration and type of parenteral nutritional support. Within the hepatocyte, the regulatory enzyme farsanoid receptor X (FXR) appears to play a pivotal role in the development of cholestasis. Recent studies have shown that its activity is suppressed by sepsis, and by plant phytosterols found in soy-based lipid preparations. This paradigm is reflected in the emerging consensus for the care of post-surgical neonates, which is based around a multi-disciplinary team approach. Using an algorithm-driven approach, an appropriate balance between caloric support and prevention of IFALD can be achieved.

CONCLUSIONS

Further prospective studies are required to further refine the optimal sequence of use of these therapies and the long-term effects on neurological development and hepatic function. However, with optimal care, the number of IF patients progressing to end-stage liver disease because of IFALD should be very low.

Robotic-assisted minimally invasive surgery of the spine (RAMISS): a proof-of-concept study using carbon dioxide insufflation for multilevel posterior vertebral exposure via a sub-paraspinal muscle working space

BACKGROUND

Open posterior spinal procedures involve extensive soft tissue disruption, increased hospital length of stay, and disfiguring scars. Our aim was to demonstrate the feasibility of using robotic-assistance for minimally invasive exposure of the posterolateral spine with and without carbon dioxide (CO₂ ) insufflation.

METHODS

Sheep specimens underwent minimally invasive subperiosteal dissection of the spine during three trials. The da Vinci S Surgical system was used for access with and without working space support via CO₂ insufflation.

RESULTS

Without insufflation, a sub-paraspinal muscle tunnel measuring 16 cm was developed between two 5 cm incisions. With insufflation, the one-sided tunnel length was 12.5 cm but without the soft tissue trauma and obstructed visualization experienced without CO₂ .

CONCLUSIONS

The use of robot-assistance for minimally invasive access to the posterior spine appears to be feasible. The use of CO₂ insufflation greatly improved our ability to visualize and access the posterior vertebral elements.

Safety and Dosing Study of Glucagon-Like Peptide 2 in Children With Intestinal Failure

BACKGROUND AND AIMS

A glucagon-like peptide 2 (GLP-2) analogue is approved for adults with intestinal failure, but no studies of GLP-2 have included children. This study examined the pharmacokinetics, safety, and nutritional effects of GLP-2 in children with intestinal failure.

METHODS

Native human GLP-2(1-33) was synthesized following good manufacturing practices. In an open-label trial, with parental consent, 7 parenteral nutrition-dependent pediatric patients were treated with subcutaneous GLP-2 (20 µg/kg/d) for 3 days (phase 1) and, if tolerated, continued for 42 days (phase 2). Nutritional treatment was directed by the primary caregivers. Patients were followed to 1 year.

RESULTS

Seven patients were enrolled (age: 4.0 ± 0.8 years; bowel length, mean ± SEM: 24% ± 4% of predicted). All were parenteral nutrition dependent since birth, receiving 44% ± 5% of calories by parenteral nutrition. GLP-2 treatment had no effect on vital signs (blood pressure, heart rate, and temperature) and caused no significant adverse events. Peak GLP-2 levels were 380 pM (day 3) and 295 pM (day 42), with no change in half-life or endogenous GLP-2 levels. Nutritional indices showed a numeric improvement in z scores and citrulline levels; the z score was maintained while citrulline levels returned to baseline once GLP-2 was discontinued.

CONCLUSIONS

GLP-2 was well tolerated in children, with a pharmacokinetic profile similar to that of adults. There were no changes in endogenous GLP-2 release or metabolism. These results suggest that GLP-2 ligands may be safely used in pediatric patients; larger trials are suggested to investigate nutritional effects.

Glucagon-Like Peptide-2 Alters Bile Acid Metabolism in Parenteral Nutrition--Associated Liver Disease

BACKGROUND

We aim to study the mechanisms underlying our previous finding that exogenous glucagon-like peptide-2 (GLP-2) treatment in a preclinical model of neonatal parenteral nutrition-associated liver disease (PNALD) improves cholestasis.

METHODS

Neonatal piglets received 17 days of parenteral nutrition (PN) therapy and either saline control (PN/Saline n = 8) or GLP-2 treatment at 11 nmol/kg/d (PN/GLP-2, n = 7). At terminal laparotomy, bile and liver samples were collected. The relative gene expression of enzymes involved in bile acid synthesis, regulation, and transport was measured in liver by reverse-transcriptase quantitative polymerase chain reaction. Bile acid composition in bile was determined using tandem mass spectrometry. Data were analyzed using 1-way analysis of variance (ANOVA) or Kruskal-Wallis ANOVA.

RESULTS

GLP-2 increased the expression of bile acid export genes: multidrug resistance-associated proteins 2 (MRP2) (P = .002) and 3 (MRP3) (P = .037) over saline control. GLP-2 increased expression of Farnesoid X receptor (FXR) (P < .001) and CYP7A1 (cytochrome P450, family 7, subfamily A, polypeptide 1) (P = .03). GLP-2 treatment was associated with decreased concentrations of taurohyocholic acid and conjugates of toxic lithocholic acid (P < .01). GLP-2 treatment increased the liver bile acid content.

CONCLUSIONS

GLP-2 treatment was associated with alterations in the hepatic expression of genes involved in bile acid metabolism. The transcriptomic results indicate the mechanisms at the transcriptional level acting to regulate bile acid synthesis and increase bile acid export. Differences in bile acid profiles further support a beneficial role for GLP-2 therapy in PNALD.

Animal models of gastrointestinal and liver diseases. Animal models of infant short bowel syndrome: translational relevance and challenges

Intestinal failure (IF), due to short bowel syndrome (SBS), results from surgical resection of a major portion of the intestine, leading to reduced nutrient absorption and need for parenteral nutrition (PN). The incidence is highest in infants and relates to preterm birth, necrotizing enterocolitis, atresia, gastroschisis, volvulus, and aganglionosis. Patient outcomes have improved, but there is a need to develop new therapies for SBS and to understand intestinal adaptation after different diseases, resection types, and nutritional and pharmacological interventions. Animal studies are needed to carefully evaluate the cellular mechanisms, safety, and translational relevance of new procedures. Distal intestinal resection, without a functioning colon, results in the most severe complications and adaptation may depend on the age at resection (preterm, term, young, adult). Clinically relevant therapies have recently been suggested from studies in preterm and term PN-dependent SBS piglets, with or without a functional colon. Studies in rats and mice have specifically addressed the fundamental physiological processes underlying adaptation at the cellular level, such as regulation of mucosal proliferation, apoptosis, transport, and digestive enzyme expression, and easily allow exogenous or genetic manipulation of growth factors and their receptors (e.g., glucagon-like peptide 2, growth hormone, insulin-like growth factor 1, epidermal growth factor, keratinocyte growth factor). The greater size of rats, and especially young pigs, is an advantage for testing surgical procedures and nutritional interventions (e.g., PN, milk diets, long-/short-chain lipids, pre- and probiotics). Conversely, newborn pigs (preterm or term) and weanling rats provide better insights into the developmental aspects of treatment for SBS in infants owing to their immature intestines. The review shows that a balance among practical, economical, experimental, and ethical constraints will determine the choice of SBS model for each clinical or basic research question.

Rising post-colectomy complications in children with ulcerative colitis despite stable colectomy rates in United States

BACKGROUND AND AIMS

In children with ulcerative colitis, data on temporal colectomy trends and in-hospital post-colectomy complications are limited. Thus, we evaluated time trends in colectomy rates and post-colectomy complications in children with ulcerative colitis.

METHODS

We identified all children (≤18years) with a diagnosis code of ulcerative colitis (ICD-9: 556.X) and a procedure code of colectomy (ICD-9: 45.8 and 45.7) in the Kids' Inpatient Database for 1997, 2000, 2003, 2006 and 2009. The incidence of colectomies for pediatric ulcerative colitis was calculated and Poisson regression analysis was performed to evaluate the change in colectomy rates. In-hospital postoperative complication rates were assessed and predictors for postoperative complications were evaluated using multivariate logistic regression.

RESULTS

The annual colectomy rate in pediatric ulcerative colitis was 0.43 per 100,000person-years, which was stable throughout the study period (P>.05). Postoperative complications were experienced in 25%, with gastrointestinal (13%) and infectious (9.3%) being the most common. Postoperative complication rates increased significantly by an annual rate of 1.1% from 1997 to 2009 (P=.01). However, other independent predictors of postoperative complications were not identified. Patients with postoperative complications had significantly longer median length of stay (14.3days vs 8.2days; P<.001) and higher median hospital charges per patient (US $81,567 vs US $55,461; P<.001) compared to those without complications.

CONCLUSION

Colectomy rates across the United States in children with ulcerative colitis have remained stable between 1997 and 2009; however, in-hospital postoperative complication rates have increased.

Glucagon-Like Peptide 2 Improves Cholestasis in Parenteral Nutrition--Associated Liver Disease

BACKGROUND

Parenteral nutrition-associated liver disease (PNALD) remains a significant cause of morbidity and mortality in neonates with intestinal failure. Although glucagon-like peptide-2 (GLP-2) is being advanced as therapy, the effect of GLP-2 treatment on PNALD is unknown. We aim to investigate the effect of exogenous GLP-2 administration on hepatic function in a neonatal piglet model of PNALD.

METHODS

Neonatal piglets (aged 2-6 days) underwent jugular venous catheterization to receive isonitrogenous, isocaloric parenteral nutrition (PN). Piglets were allocated to 2 groups: group 1 (n = 8) received saline while group 2 (n = 7) received GLP-2 (at 11 nmol/kg/d). After 17 days, piglets underwent terminal laparotomy, and bile flow was measured. Liver specimens were analyzed histologically and with immunoperoxidase staining. Age-matched sow-reared control piglets (group 3, n = 8) were used for comparison.

RESULTS

Both groups 1 and 2 receiving PN developed cholestasis relative to sow-reared controls, as evidenced by a decrease in bile flow and increase in serum total bilirubin. However, group 2 had improved bile flow (1.35 vs 0.73 µL/g; P = .02) and diminished bilirubin (38.0 vs 78.5 µmol/L; P = .008) compared with group 1. Group 2 also had lower serum alanine aminotransferase levels, a marker of liver injury. Histologically, the liver specimens in group 1 had marked hepatocyte pigmentation, which was decreased in group 2 specimens.

CONCLUSIONS

The exogenous administration of GLP-2 is associated with the improvement of cholestasis and liver injury. This study introduces a novel role for GLP-2 in improving PNALD in the setting of prolonged PN duration.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Effects of chronic glucagon-like peptide-2 therapy during weaning in neonatal pigs

BACKGROUND

The enteroendocrine hormone glucagon like peptide-2 (GLP-2) and its ligands are under development as therapeutic agents for a variety of intestinal pathologies. A number of these conditions occur in neonates and infants, and thus a detailed understanding of the effects of GLP-2 during the phase of rapid growth during infancy is required to guide the development of therapeutic applications. We studied the effects of GLP-2 in the neonatal pig to determine the potential effects of exogenous administration.

METHODS

Two day old newborn domestic piglets were treated with GLP-2 (1-33) at 40 μg/kg/day or control drug vehicle (saline), by subcutaneous injection, given in two doses per day, (n=6/group) for 42 days. Animals were weaned normally, over days 21-25. In the fifth week of life, they underwent neuro-developmental testing, and a pharmacokinetic study. On day 42, they were euthanized, and a complete necropsy performed, with histological assessment of tissues from all major organs.

RESULTS

GLP-2 treatment was well tolerated, one control animal died from unrelated causes. There were no effects of GLP-2 on weight gain, feed intake, or behavior. In the treated animals, GLP-2 levels were significantly elevated at 2400±600 pM while at necropsy, organ weights and histology were not affected except in the intestine, where the villus height in the small intestine and the crypt depth, throughout the small intestine and colon, were increased. Similarly, the rate of crypt cell proliferation (Ki-67 staining) was increased in the GLP-2 treated animals and the rate of apoptosis (Caspase-3) was decreased, the depth of the microvilli was increased and the expression of the mRNA for the GLP-2 receptor was decreased throughout the small and large intestine.

CONCLUSIONS

In these growing animals, exogenous GLP-2 at pharmacologic doses was well tolerated, with effects confined to the gastrointestinal tract.

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

BACKGROUND⁄

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Effects of sleeve gastrectomy and ileal transposition, alone and in combination, on food intake, body weight, gut hormones, and glucose metabolism in rats

Bariatric surgeries are hypothesized to produce weight loss and improve diabetes control by multiple mechanisms including gastric restriction and lower gut stimulation; the relative importance of these mechanisms remains poorly understood. We compared the effects of a typical foregut procedure, sleeve gastrectomy, (SG) with a primarily hindgut surgery, ileal transposition (IT), alone and together (SGIT), or sham manipulations, on food intake, body weight, gut hormones, glucose tolerance, and key markers of glucose homeostasis in peripheral tissues of adult male Sprague-Dawley rats (450-550 g, n = 7-9/group). SG, IT, and SGIT surgeries produced transient reduction in food intake and weight gain; the effects of SG and IT on intake and body weight were nonadditive. SG, IT, and SGIT surgeries resulted in increased tissue expression and plasma concentrations of the lower gut hormones glucagon-like peptide-1 and peptide YY and decreased plasma glucose-dependent insulinotropic peptide, insulin, and leptin concentrations. Despite transient effects on intake and weight gain, the SG, IT, and SGIT surgeries produced a significant improvement in glucose tolerance. In support of glycemic improvements, the protein abundance of key markers of glucose metabolism (e.g., GLUT4, PKA, IRS-1) in muscle and adipose tissue were increased, whereas the expression of key gluconeogenic enzyme in liver (G-6-Pase) were decreased following the surgeries. Therefore, our data suggest that enhanced lower gut stimulation following SG, IT, and SGIT surgeries leads to transient reduction in food intake and weight gain together with enhanced secretion of lower gut hormones and improved glucose clearance by peripheral tissues.

Effects of polymeric formula vs elemental formula in neonatal piglets with short bowel syndrome

BACKGROUND

Intestinal adaptation is important for recovery in short bowel syndrome (SBS). This process is dependent on the presence of enteral nutrition (EN) and trophic factors, such as glucagon-like peptide-2 (GLP-2). In clinical practice, elemental formula is often used to feed neonates with SBS, whereas animal studies suggest polymeric formula promotes better intestinal adaptation. In neonatal piglet models of SBS, with or without ileum, we compared the elemental with the polymeric formula, including the effect on endogenous GLP-2.

MATERIALS AND METHODS

Forty-eight piglets underwent 75% mid-intestinal resection with jejunoileal anastomosis, 75% distal-intestinal resection with jejunocolic anastomosis (JC), or sham without resection. Parenteral nutrition (PN) started postoperatively, tapering as EN was increased, according to clinical criteria, based on diarrhea and weight. Within groups, piglets were randomized to an isocaloric/isonitrogenous elemental (amino acid) or polymeric (intact protein) diet. Plasma GLP-2 and histology for adaptation were measured at 14 days.

RESULTS

Within both SBS and control groups, no difference in adaptation was observed according to diet. A difference was observed only within the JC piglet group with regard to clinical outcomes. In these piglets, compared with elemental formula, the polymeric formula was associated with more diarrhea ( P = .023) and longer duration of PN support (P = .047).

CONCLUSION

An overall benefit of the polymeric formula over the elemental formula on gut adaptation was not observed. Furthermore, SBS piglets without ileum had less ability to tolerate polymeric formula, contributing to more days of PN support.

Early feeding in pediatric patients following stoma closure in a resource limited environment

BACKGROUND

Establishment of enteral nutrition is necessary after intestinal surgery. In resource-strained environments, it can be critical. This study examined the effect of early feeding in pediatric patients undergoing stoma closure in a country with mid-level socioeconomic indices.

METHODS

With parenteral consent and ethics board approval, patients were prospectively enrolled in early feeding (Group 1), starting feeds 24h post-operation with a protocol driven increase. They were compared with similar patients managed without a specific protocol over the 12 months prior (Group 2).

RESULTS

There were 31 patients in each group with similar mean age and weight. The mean first sustained feed was achieved at 28.5 ± 4.4 h* in Group 1 vs. 153.8 ± 28.6 h in Group 2. Full feeds were achieved within 62.3 ± 19.2 h* vs. 196.0 ± 40.5 h in Group 1 and 2, respectively. Mean hospital stay was 7.2 days* in Group 1 vs. 9.4 days in Group 2. A reduction in postoperative fever and wound infections was observed in Group 1 (*p<0.05).

CONCLUSION

Early enteral feeding after elective bowel anastomosis is well tolerated in children and results in shorter hospital stay and fewer complications.

Longer term effects of closed repair of pectus excavatum on cardiopulmonary status

BACKGROUND

The "Nuss" repair is done for correction of moderate to severe pectus excavatum (PE). The long term cardiopulmonary and psychosocial effects of repair are uncertain. The objective of this study was to compare cardiopulmonary function and subjective evaluation of appearance and exercise tolerance pre-bar insertion with post-bar removal.

METHODS

All patients underwent preoperative and post-bar (3 month) removal evaluation with complete pulmonary function tests, exercise stress testing, echocardiogram, and self-rated appearance and exercise tolerance scoring. The protocol was approved by the regional ethics board, and all families gave informed consent.

RESULTS

Sixty-seven patients underwent pre and post testing. Preoperative CT index was 4.4 ± 1.3. Cardiopulmonary outcomes, standardized for height and weight, showed significant improvements in FEV-1 as (pre) 81.1 ± 17.0 vs post 89.8 ± 20.5*, FVC: 91.2 ± 18.6 vs 98.9 ± 22.9*, O2 pulse: 75.8 ± 14.4 vs 80.5 ± 18.3* (each as % predicted). Both the self-ratings of appearance (2.5 ± 0.8 vs 4.4 ± 0.5) and ability to exercise (3.3 ± 0.7 vs 4.3 ± 0.6, scale 1-5) increased significantly. (All data: mean ± St Dev, *p<0.05) CONCLUSIONS: Closed repair of PE results in improvements in pulmonary and aerobic exercise function and perceived appearance and exercise tolerance. Our data suggest that the impact on appearance and self-perceived well being is greater than the physical effect.

Bracing is an effective therapy for pectus carinatum: interim results

BACKGROUND

Pectus Carinatum is a common congenital chest wall malformation. Until recently the mainstay of treatment was surgical remodeling of the deformed chest wall. Initial results suggest that non-operative bracing may be an effective therapy, but the optimal strategy for correction is not known. Herein we report the results of a self-adjustable low profile bracing system worn continuously until the defect is corrected (correction phase), then worn at night (8 h/day) until completion of axial growth (maintenance phase)-the Calgary Protocol.

METHODS

Patients referred to a pediatric surgery chest wall clinic were prospectively asked to join an IRB approved outcomes monitoring study. 124 patients were evaluated from 2007 to 2011, and 98 were prescribed a brace and counseled to follow the protocol.

RESULTS

98 patients consented to follow-up at starting bracing age: 14.4 ± 1.9 years, Tanner stage: 3.6 ± 0.5, protrusion: 2.1 ± 1.0 cm, self-rating of appearance: 2.9 ± 1.1, and exercise tolerance: 4.4 ± 1.1 (1-5 with 5 = normal). 10 patients are in correction phase, and 44 patients have completed correction after 7.0 ± 7.3 months: Tanner stage: 3.8 ± 0.1, protrusion: 0.5 ± 0.6 cm*, appearance: 4.3 ± 0.3* and exercise tolerance 4.6 ± 1.0. Correction occurred more quickly in patients prior to achieving Tanner stage IV (4.2 ± 0.9 months) vs. Tanner stage IV (8.0 ± 7.1 months) at the beginning of bracing. 21 patients completed maintenance bracing after 17.9 ± 19.0 months: Tanner stage: 3.9 ± 0.2, protrusion 0.5 ± 0.7 cm*, appearance: 4.3 ± 0.9*, and exercise tolerance: 4.8 ± 1.4. Average follow-up after bracing is 13.9 ± 16.0 months (mean ± S.D., *P < .05). There was one recurrence, likely due to early discontinuation of maintenance. This responded to an additional 6 months of bracing. 42 patients failed therapy secondary to non-compliance or were lost in follow up, while 2 patients did not respond to bracing and required open operation.

CONCLUSIONS

If patients are compliant, a self- adjusting brace system can give rapid correction of the pectus carinatum protrusion with excellent patient satisfaction. These interim results suggest that continued bracing until skeletal maturity gives long term durability to the correction. Further studies will be required to further refine this promising therapy.

Glucagon-like peptide 2 induces vasoactive intestinal polypeptide expression in enteric neurons via phophatidylinositol 3-kinase-γ signaling

Glucagon-like peptide 2 (GLP-2) is an enteroendocrine hormone trophic for intestinal mucosa; it has been shown to increase enteric neuronal expression of vasoactive intestinal polypeptide (VIP) in vivo. We hypothesized that GLP-2 would regulate VIP expression in enteric neurons via a phosphatidylinositol-3 kinase-γ (PI3Kγ) pathway. The mechanism of action of GLP-2 was investigated using primary cultures derived from the submucosal plexus (SMP) of the rat and mouse colon. GLP-2 (10(-8) M) stimulation for 24 h increased the proportion of enteric neurons expressing VIP (GLP-2: 40 ± 6% vs. control: 22 ± 5%). GLP-2 receptor expression was identified by immunohistochemistry on neurons (HuC/D+) and glial cells (GFAP+) but not on smooth muscle or fibroblasts in culture. Over 1-4 h, GLP-2 stimulation of SMP increased phosphorylated Akt/Akt ratios 6.1-fold, phosphorylated ERK/ERK 2.5-fold, and p70S6K 2.2-fold but did not affect intracellular cAMP. PI3Kγ gene deletion or pharmacological blockade of PI3Kγ, mammalian target of rapamycin (mTOR), and MEK/ERK pathways blocked the increase in VIP expression by GLP-2. GLP-2 increased the expression of growth factors and their receptors in SMP cells in culture [IGF-1r (3.2-fold increase), EGFr (5-fold), and ErbB-2-4r (6- to 7-fold)] and ligands [IGF-I (1.5-fold), amphiregulin (2.5-fold), epiregulin (3.2-fold), EGF (7.5-fold), heparin-bound EGF (2.0-fold), β-cellulin (50-fold increase), and neuregulins 2-4 (300-fold increase) (by qRT-PCR)]. We conclude that GLP-2 acts on enteric neurons and glial cells in culture via a PI3Kγ/Akt pathway, stimulating neuronal differentiation via mTOR and ERK pathways, and expression of receptors and ligands for the IGF-I and ErbB pathways.

Comparison of the effects of Roux-en-Y gastric bypass and ileal transposition surgeries on food intake, body weight, and circulating peptide YY concentrations in rats

BACKGROUND

Roux-en-Y gastric bypass (RYGB) surgery is one of the most effective treatments for obesity producing long-term weight loss. The anorexia and weight loss from RYGB could be due to gastric restriction, malabsorption, enhanced lower gut stimulation, increased energy expenditure, and/or other metabolic adaptations. In ileal transposition (IT) surgery, a segment of the ileum is transposed to the upper jejunum with no gastric restriction or malabsorption. Our objective is to compare the effects of RYGB and IT surgeries on food intake, body weight, and plasma concentrations of the anorexigenic lower gut hormone Peptide YY (PYY) in rats.

METHODS

Adult male Sprague-Dawley rats were subjected to either RYGB (n = 9), IT (n = 9) or sham surgeries (n = 16). A subset of sham animals were either pair-fed to RYGB (n = 9) or ad lib fed (n = 7) on a highly palatable mixed nutrient liquid food (Ensure). Food intake, body weight and plasma PYY concentrations were measured.

RESULTS

The data demonstrate that (1) RYGB produces a sustained reduction in food intake and weight gain, (2) the anorexic effects of IT are relatively transient lasting for 5 weeks, (3) the reduction in weight gain resulting from IT is similar to that of animals pair-fed to RYGB, and (4) RYGB and IT surgeries are associated with elevated postprandial plasma PYY concentrations.

CONCLUSIONS

We demonstrate in our rat models that RYGB surgery produces a greater reduction in food intake and weight gain than IT surgery, and that both surgeries are associated with enhanced plasma concentrations of Peptide YY.

The effects of glucagon-like peptide 2 on enteric neurons in intestinal inflammation

BACKGROUND

Intestinal inflammation alters the structure and function of the enteric nervous system (ENS). Glucagon-like peptide 2 (GLP-2) reduces intestinal inflammation and has trophic effects on isolated neurons. This study examined the effects of GLP-2 treatment on the submucosal plexus of rat colon in the trinitrobenzene sulfonic acid (TNBS) model of colitis.

METHODS

After administration of TNBS or saline/ethanol for controls, animals were allocated to treatment with GLP-2 (50 μg kg⁻¹ day⁻¹, s.c.) or sham injection of vehicle, twice daily. Animals were monitored, following clinical parameters, and killed on day 5. The number of neuronal cell bodies per ganglion was quantified using immunohistochemistry on submucosal whole mount preparations, with further characterization of specific subpopulations using antibodies against vasoactive intestinal polypeptide (VIP), neuronal nitric oxide synthase (nNOS), and enteric glial cells with glial fibrillary acid protein and S100.

KEY RESULTS

Glucagon-like peptide 2 treatment was associated with a significant amelioration of weight loss, and reduced neutrophil infiltration and microscopic colitis scores in the TNBS animals. Inflammation resulted in a loss of enteric neurons in submucosal ganglia; GLP-2 treatment restored the enteric neuronal populations to normal. In control, non-inflamed animals, GLP-2 treatment increased the number of VIP expressing neurons per ganglion; in TNBS-treated animals, GLP-2 prevented an inflammation-induced reduction in the numbers of VIP expressing neurons per ganglion. Glucagon-like peptide 2 did not change the numbers of nNOS neurons or enteric glial cells in either the control, or inflamed state.

CONCLUSIONS & INFERENCES

These findings show that GLP-2 increased the number of VIP expressing neurons in normal animals, and prevents the inflammation-induced loss of neurons in the colonic submucosal ganglia, with an increase in the proportion of VIP expressing neurons. They suggest that GLP-2 may have a role in protecting or regulating the circuitry of the ENS under basal and inflamed states.

The influence of nutrients, biliary-pancreatic secretions, and systemic trophic hormones on intestinal adaptation in a Roux-en-Y bypass model

PURPOSE

The signals that govern the upregulation of nutrient absorption (adaptation) after intestinal resection are not well understood. A Gastric Roux-en-Y bypass (GRYB) model was used to isolate the relative contributions of direct mucosal stimulation by nutrients, biliary-pancreatic secretions, and systemic enteric hormones on intestinal adaptation in short bowel syndrome.

METHODS

Male rats (350-400 g; n = 8/group) underwent sham or GRYB with pair feeding and were observed for 14 days. Weight and serum hormonal levels (glucagon-like peptide-2 [GLP-2], PYY) were quantified. Adaptation was assessed by intestinal morphology and crypt cell kinetics in each intestinal limb of the bypass and the equivalent points in the sham intestine. Mucosal growth factors and expression of transporter proteins were measured in each limb of the model.

RESULTS

The GRYB animals lost weight compared to controls and exhibited significant adaptive changes with increased bowel width, villus height, crypt depth, and proliferation indices in the alimentary and common intestinal limbs. Although the biliary limb did not adapt at the mucosa, it did show an increased bowel width and crypt cell proliferation rate. The bypass animals had elevated levels of systemic PYY and GLP-2. At the mucosal level, insulin-like growth factor-1 (IGF-1) and basic fibroblast growth factor (bFGF) increased in all limbs of the bypass animals, whereas keratinocyte growth factor (KGF) and epidermal growth factor (EGF) had variable responses. The expression of the passive transporter of glucose, GLUT-2, expression was increased, whereas GLUT-5 was unchanged in all limbs of the bypass groups. Expression of the active mucosal transporter of glucose, SGLT-1 was decreased in the alimentary limb.

CONCLUSIONS

Adaptation occurred maximally in intestinal segments stimulated by nutrients. Partial adaptation in the biliary limb may reflect the effects of systemic hormones. Mucosal content of IGF-1, bFGF, and EGF appear to be stimulated by systemic hormones, potentially GLP-2, whereas KGF may be locally regulated. Further studies to examine the relationships between the factors controlling nutrient-induced adaptation are suggested. Direct contact with nutrients appears to be the most potent factor in inducing mucosal adaptation.

Meal-induced hormone responses in a rat model of Roux-en-Y gastric bypass surgery

Roux-en-Y gastric bypass (RYGB) surgery is the most effective treatment for morbid obesity and remission of associated type 2 diabetes, but the mechanisms involved are poorly understood. The aim of the present study was to develop and validate a rat model for RYGB surgery that allows repeated measurement of meal-induced changes in gut and pancreatic hormones via chronic venous catheters. Male Sprague Dawley rats made obese on a palatable high-fat diet were subjected to RYGB or sham surgery and compared with chow-fed, lean controls. Hormonal responses to a mixed-liquid test meal were examined by frequent blood sampling through chronically implanted jugular catheters in freely behaving rats, 3-4 months after surgery, when RYGB rats had significantly reduced body weight and fat mass compared with sham-operated rats. Hyperleptinemia, basal hyperinsulinemia, and hyperglycemia as well as postprandial glucose intolerance seen in sham-operated, obese rats were completely reversed by RYGB and no longer different from lean controls. Postprandial increases in glucagon-like peptide-1, peptide YY, and amylin as well as suppression of ghrelin levels were all significantly augmented in RYGB rats compared with both sham-operated obese and lean control rats. Thus, our rat model replicates most of the salient hormonal and glycemic changes reported in obese patients after RYGB, with the addition of amylin to the list of potential candidate hormones involved in hypophagia, weight loss, and remission of diabetes. The model will be useful for elucidating the specific peripheral and central mechanisms involved in the suppression of appetite, loss of body weight, and remission of type 2 diabetes.

The assessment, and glucagon-like peptide-2 modulation, of intestinal absorption and function

The treatment of patients with short bowel syndrome is hampered by a lack of treatment and measurement methods. This article reviews our evolving understanding of the role of glucagon-like peptide 2 (GLP-2) in controlling the adaptive process. The ability of the remnant intestine to produce GLP-2 appears to be predictive of the adaptive process; exogenous GLP-2 may be a therapy to augment adaptation. Strategies for monitoring patients, including conventional means, such as anthropomorphic measurements, plasma levels of specific nutrients, and vitamins and radiological contrast studies are reviewed. Investigational methods, such as nutrient balance studies, plasma citrulline levels, and the absorption of inert sugars (3-0 methyl glucose, mannitol, and lactulose) are discussed with the evidence to support their use.

Relationship between biopsy-proven parenteralnutrition-associated liver fibrosis and biochemical cholestasis in children with short bowel syndrome

PURPOSE

The aim of the study was to determine the frequency of biochemical cholestasis (direct bilirubin [DB] > or =2 mg/dL) in children with short bowel syndrome and biopsy-proven parenteral nutrition (PN)-associated liver disease and to define predictive factors for the occurrence and degree of hepatic fibrosis.

METHODS

After institutional review board approval, a retrospective review was conducted of patients followed by 2 multidisciplinary intestinal rehabilitation programs between January 1, 2000, and September 30, 2008. Inclusion criteria were exposure to PN (>30 days) and having undergone a liver biopsy. Liver biopsy specimens were graded from 0 to 3 based upon degree of fibrosis in the pathology report. The most recent DB within 10 days before biopsy was recorded.

RESULTS

A total of 66 children underwent 83 liver biopsy procedures. The most common diagnoses included necrotizing enterocolitis (NEC) (36.4%), gastroschisis (22.7%), and intestinal atresia (15.1%). Median age at biopsy was 6.1 months with a median duration of PN of 4.7 months. Of the patients, 70.3% had a history of exposure to parenteral omega-3 lipid emulsion. Of the liver biopsy specimens, 89% (74/83) demonstrated some degree of fibrosis (fibrosis scale 1-3), including 9.6% (8/83) with evidence of cirrhosis. 83% of biopsies without fibrosis and 55% of biopsies with fibrosis were obtained in patients without evidence of biochemical cholestasis (P = .20). Three (37%) of the 8 patients with cirrhosis on liver biopsy had no evidence of biochemical cholestasis. Univariate analysis identified only gestational age (GA) at birth as significantly associated with the degree of liver fibrosis (P = .03). A multivariate logistic regression model accounting for multiple biopsy procedures in patients revealed that GA was a predictor of fibrosis only in patients with a diagnosis other than NEC (P < .01).

CONCLUSIONS

In children with short bowel syndrome, biochemical cholestasis does not reflect the presence or degree of histologically confirmed PN-associated liver fibrosis. Careful follow-up, combined with further refinement of diagnostic and hepatoprotective strategies, may be warranted in this patient population.

Meal patterns, satiety, and food choice in a rat model of Roux-en-Y gastric bypass surgery

Gastric bypass surgery efficiently and lastingly reduces excess body weight and reverses type 2 diabetes in obese patients. Although increased energy expenditure may also play a role, decreased energy intake is thought to be the main reason for weight loss, but the mechanisms involved are poorly understood. Therefore, the aim of this study was to characterize the changes in ingestive behavior in a rat model of Roux-en-Y gastric bypass surgery (RYGB). Obese (24% body fat compared with 18% in chow-fed controls), male Sprague-Dawley rats maintained for 15 wk before and 4 mo after RYGB or sham-surgery on a two-choice low-fat/high-fat diet, were subjected to a series of tests assessing energy intake, meal patterning, and food choice. Although sham-operated rats gained an additional 100 g body wt during the postoperative period, RYGB rats lost approximately 100 g. Intake of a nutritionally complete and palatable liquid diet (Ensure) was significantly reduced by approximately 50% during the first 2 wk after RYGB compared with sham surgery. Decreased intake was the result of greatly reduced meal size with only partial compensation by meal frequency, and a corresponding increase in the satiety ratio. Similar results were obtained with solid food (regular or high-fat chow) 6 wk after surgery. In 12- to 24-h two-choice liquid or solid diet paradigms with nutritionally complete low- and high-fat diets, RYGB rats preferred the low-fat choice (solid) or showed decreased acceptance for the high-fat choice (liquid), whereas sham-operated rats preferred the high-fat choices. A separate group of rats offered chow only before surgery completely avoided the solid high-fat diet in a choice paradigm. The results confirm anecdotal reports of "nibbling" behavior and fat avoidance in RYGB patients and provide a basis for more mechanistic studies in this rat model.

Nutritional effects of the serial transverse enteroplasty procedure in experimental short bowel syndrome

BACKGROUND/PURPOSE

The serial transverse enteroplasty (STEP) procedure appears beneficial clinically, but the mechanism(s) underlying these effects remains unclear. The present study evaluated the nutritional, hormonal, and morphologic effects of the STEP procedure in a rodent model of short bowel syndrome.

METHODS

With institutional animal care ethics approval, Sprague-Dawley rats underwent an 80% distal bowel resection, anastomosing the 30 cm remnant of jejunum to the ascending colon; at day 14, animals were randomly assigned to control or a STEP procedure (n = 8/group). Animals were pair-fed with normal chow; after a further 3 weeks, intestinal transit, hormonal and metabolic balance studies were done, and intestinal tissues were taken for analysis.

RESULTS

The STEP group had increased weight gain (resected: -0.34% +/- 2.9% vs STEP: 2.5% +/- 1.5%), increased bowel length (34.1 +/- 1.5 vs 36.9 +/- 2.2 cm), increased jejunal villus height (555 +/- 59 vs 635 +/- 65 microm), decreased rates of crypt cell apoptosis, increased expression of mRNA for the GLP-2 receptor, and increased postprandial production of glucagon-like peptide 2 (45 +/- 14 vs 65 +/- 12 pmol/L) (P < .05 by Student t test). There were no differences in intestinal transit; absorption of total calories, protein, fat, or carbohydrate; crypt cell proliferation rates; or the expression of intestinal transporter proteins (SGLT-1, GLUT-2, and GLUT-5).

CONCLUSIONS

The STEP procedure improves weight gain and augments gross and microscopic intestinal morphology in severe experimental short bowel syndrome. Postprandial GLP-2 levels are increased, as is the expression of the GLP-2 receptor; these mechanisms may contribute to these metabolic effects and may be useful in guiding the use of the STEP procedure clinically.

Operative innovation to the "Nuss" procedure for pectus excavatum: operative and functional effects

BACKGROUND

The "Nuss" procedure for repair of pectus excavatum is performed with increasing frequency worldwide. We describe a technique of performing relaxing or "kerf" incisions along the cartilaginous ribs at the point of maximal chest wall concavity to facilitate retrosternal dissection and to reduce chest wall tension. The effects on operative parameters and long-term changes in cardiopulmonary function and appearance were evaluated prospectively.

METHODS

Thirty patients underwent a Nuss procedure for the period from 2001 to 2004. Fifteen patients underwent a modified Nuss (MN) with sternocostal "relaxing" incisions, and these were compared to 15 patients undergoing a standard Nuss (SN). Data were prospectively gathered and included the number of relaxing incisions, bar number, blood loss, duration of epidural analgesia, number of days to discharge, and preoperative and postoperative cardiopulmonary function measures.

RESULTS

The average Haller index of the SN group was 3.9 +/- 0.7 vs MN group index of 4.6 +/- 1.6 (P < .05). The median number of relaxing incisions in the study group was 4.0 +/- 0.7 (range 3 - 8). There were no significant differences between the study groups in any of the operative parameters analyzed, including blood loss, days of epidural requirements or days to reach functional independence. Nor were there differences in the improvement in subjective appearance, complications, pulmonary function, cardiac output at rest, oxygen transport or minute ventilation at maximal exercise. Subjectively, bar positioning and the intraoperative visualization was easier with the relaxing incisions.

CONCLUSIONS

The addition of sternocostal relaxing incisions to the standard Nuss procedure appears to facilitate retrosternal dissection and bar placement, but no changes in long-term function or cosmesis were noted. The use of relaxing incisions appears to be safe and may facilitate operative visualization of retrosternal structures.

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

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

The effects of variations in dose and method of administration on glucagon like peptide-2 activity in the rat

Glucagon-like peptide-2 (GLP-2) is a potent, intestinal-specific trophic hormone. However, the relationship between the dose and timing of GLP-2 administration and these trophic effects is not clear. We investigated the effects of variations in the dose and timing of GLP-2 administration on its intestinal trophic activity. A rodent model of total parenteral nutrition (TPN) mucosal atrophy was used, examining intestinal morphology in the adult male rat after 5 days. Groups were: controls, maintained with TPN alone and GLP-2 treated groups (high dose; 240 microg/kg/day, low dose; 24 microg/kg/day) given by continuous or intermittent (over 1 h, twice daily) intravenous infusion. Body weight and total small bowel length were significantly increased in the high dose, continuous infusion group. Both high dose infusion methods increased total small bowel weight, villus height, crypt depth, and total mucosal surface area. Both high dose infusion and low dose intermittent infusion routes increased crypt cell proliferation (P<0.05 for all comparisons). Both high dose routes gave nearly equivalent exposures; low dose continuous infusion gave higher exposure but intermittent low dose infusion resulted in an increase in crypt proliferation; neither low dose method resulted in morphologic changes. There were no differences in transporter protein expression or apoptosis rates. High dose continuous infusion appears to maximally induce intestinal growth, and also increases weight gain, while high dose GLP-2 intermittent infusion results in similar morphologic effects. A threshold level for the induction of proliferative and morphologic effects was seen in the low dose groups. These observations may be relevant for planning therapeutic trials.

Functional ontogeny of the proglucagon-derived peptide axis in the premature human neonate

BACKGROUND

The regulation of intestinal growth and development in human neonates is incompletely understood, which hinders the provision of nutrients enterally. The "hindgut" hormones glucagon-like peptides 1 and 2 have been shown to play an important role in the regulation of nutrient assimilation, intestinal growth, and function.

OBJECTIVE

Our goal was to investigate the production of glucagon-like peptides 1 and 2 in premature human infants and examine the effects of prematurity and feeding on hormone release.

PATIENTS AND METHODS

With informed consent, premature infants who were admitted to a tertiary neonatal intensive care nursery (gestational age: 28-32 weeks) were monitored with weekly determinations of postprandial glucagon-like peptide 1 and 2 levels. Comparison studies with groups of normal infants and adults were performed. Hormone levels were obtained by using specific radioimmunoassay for glucagon-like peptide 1 (1-36) and glucagon-like peptide 2 (1-33), modified for small sample volumes; accurate monitoring of enteral intake was performed at all of the sampling time points.

RESULTS

Forty-five infants with a mean gestational age of 29.6 +/- 1.9 weeks were studied; fasting levels of both glucagon-like peptides 1 and 2 were elevated. There was no correlation between gestational age and glucagon-like peptide 2 output. However, both glucagon-like peptide 1 and 2 levels were correlated with the caloric value of feeds.

CONCLUSIONS

The premature human neonate has significantly higher fasting levels of glucagon-like peptides 1 and 2 compared with adults; feeding increases these levels further. These findings suggest that the proglucagon-derived peptides may have a role in normal intestinal development and nutrient handling.

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

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

Long term cardiopulmonary effects of closed repair of pectus excavatum

The closed or "Nuss" repair of pectus excavatum is widely accepted for correction of moderate to severe deformities. Patients typically report significant subjective improvements in pulmonary symptoms, and short and medium term evaluations (up to 2 years with the bar in place) suggest modest improvement to cardiac function but a decrease in pulmonary function. This study examined the effects at 3 months post-bar removal of closed repair of pectus on pulmonary function, exercise tolerance and cardiac function. Patients were followed prospectively after initial evaluation for operation. All patients underwent preoperative and post-bar removal evaluation with CT scan, complete pulmonary function and exercise testing to anaerobic threshold, as well as echocardiogram. Twenty-six patients have completed the follow up protocol. Preoperative CT index was 4.5 +/- 1.3, average age at operation was 13.2 years, and average tanner stage was 3.5 +/- 0.5. At 3 months or greater follow-up post-bar removal, patients reported an improvement in subjective ability to exercise and appearance (P < 0.05 by wilcoxin matched pairs). Objective measures of FEV1, total lung capacity, diffusing lung capacity, O(2) pulse, VO(2max), and respiratory quotient all showed significant improvement compared to preoperative values, while normalized values of cardiac index at rest did not (All values normalized for height and age, comparisons P < 0.05 by student's paired t test). These results demonstrate a sustained improvement in cardiopulmonary function after bar removal following closed repair of pectus excavatum. These findings contrast with results from previous studies following the open procedure, or with the closed procedure at earlier time points; the long term physiological effects of closed repair of pectus excavatum include improved aerobic capacity, likely through a combination of pulmonary and cardiac effects.

Alpha1-adrenoceptors down-regulate ClC-2 chloride channels in epithelial cells from the acutely denervated jejunum

Acute sympathetic denervation of the small intestine up-regulates alpha1-adrenoceptors on villus enterocytes and activation of these alpha1-adrenoceptors inhibits chloride secretion. We tested whether alpha1-adrenoceptor-mediated inhibition of chloride secretion was the result of reduced ClC-2 chloride channel expression. Phorbol myristate acetate (PMA) (a protein kinase C (PKC) activator) had no effect on ClC-2 levels. In contrast, alpha1-adrenoceptor activation significantly decreased ClC-2 protein levels in both the villus (1.58+/-0.19 to 0.75+/-0.19 arbitrary units) and crypt (1.69+/-0.15 to 0.37+/-0.23 arbitrary units) epithelial cells from the acutely denervated jejunum but not innervated controls. These data suggest that inhibition of chloride secretion following alpha1-adrenoceptor activation in the acutely denervated small intestine may be through ClC-2 down-regulation.

Acute denervation alters the epithelial response to adrenoceptor activation through an increase in alpha1-adrenoceptor expression on villus enterocytes

Loss of sympathetic input due to intestinal denervation results in hypersensitivity and increased intestinal secretion. It is unknown whether denervation-induced alterations in intestinal epithelial physiology are the result of changes in adrenoceptors on enterocytes (ENTs). The purpose of this study was to examine adrenoceptor distribution and pharmacology on small intestinal ENTs following acute intestinal denervation. Lewis rats underwent small bowel transplantation (SBT) or sham operation and proximal small intestinal segments were harvested 1, 2 and 4 weeks postoperatively. Intestinal electrolyte movement was assessed using short-circuit current (Isc) measurements of stripped epithelial sheets following stimulation with phenylephrine (PE), an alpha(1)-adrenoceptor agonist. The presence of adrenoceptor subtypes on separated villus and crypt ENTs was assessed using flow cytometry. Alpha(1)-adrenoceptors were found on approximately 27% of jejunal villus ENTs, but not crypt ENTs, following acute extrinsic denervation. ENTs from the Lewis rat have few beta-adrenoceptors. Alpha(1)-adrenoceptor stimulation of acutely denervated intestinal epithelial sheets decreased Isc by -13.45%. This effect was mediated by a reduction in chloride (Cl(-)) secretion; the absence of Cl(-) reversed the Isc to +13.79%. In conclusion, loss of sympathetic innervation to the gastrointestinal epithelium causes acute upregulation of alpha(1)-adrenoceptors on villus ENTs, leading to inhibition of Cl(-) secretion at the villus tip. The increase in adrenoceptors may reflect a compensatory mechanism to combat the increased secretory state of the bowel due to the loss of the sympathetic innervation and tonic control over intestinal secretion.

Glucagon-like peptide-2 induces a specific pattern of adaptation in remnant jejunum

Glucagon-like peptide-2 (GLP-2) is an enteroendocrine hormone which is uniquely trophic for the intestine; a physiological role in regulating nutrient absorptive capacity is becoming apparent. GLP-2, independent of enteral feeding, stimulates a classical pattern of intestinal adaptation in terminal ileum following resection. Herein we investigate the effects of GLP-2 on the jejunal remant using a rat model of short bowel syndrome (SBS). Juvenile 250- to 275-g SD rats underwent 80% distal small bowel resection, leaving 20 cm of proximal jejunum and venous catheterization. Animals were maintained with total parenteral nutrition (TPN) or TPN+10 microg/kg/hr GLP-2 (n=8 per group). After 7 days, intestinal permeability was assessed by urinary recovery of gavaged carbohydrate probes. Animals were euthanized, and the intestines taken for analysis of morphology, crypt cell proliferation, apoptosis, and expression of SGLT-1 and GLUT-5 transport proteins. GLP-2 treatment reduced intestinal permeability and increased in vivo glucose absorption, small intestinal weight, surface area, villus height, crypt depth, and microvillus height. Intestinal mucosal DNA and protein content per unit length of the small bowel were increased (P < 0.05 for all comparisons). However, in contrast to previous studies examining GLP-2's effects on remnant ileum, the jejunal crypt apoptotic index was increased in GLP-2-treated animals, with no increase in SGLT-1 or GLUT 5 expression. These results show that exogenous GLP-2 treatment of animals with jejunal remnant reduces intestinal permeability, increases glucose absorption, and stimulates morphological features of intestinal adaptation including increased micovillus height and surface area. However, the pattern of changes seen is different from that in remnant ileum. This suggests that GLP-2's effects are specific to different regions of the bowel. Nonetheless, remnant jejunum is responsive to GLP-2 in the absence of enteral nutrition. Further studies are warranted to establish the mechanisms of action and therapeutic potential of GLP-2 in modulating nutrient absorptive capacity.

Persistent post-transplant polyuria managed by bilateral native-kidney laparoscopic nephrectomy

Polyuria is not considered an absolute indication for pre-transplant nephrectomy; however, it may complicate post-transplantation fluid management. Bilateral native-kidney laparoscopic nephrectomy was performed at our centre in two patients (four kidneys) 1 month after they had received a living related-donor renal transplant. The indication for nephrectomy was severe post-transplant polyuria secondary to the patient's underlying disease: juvenile nephronophthisis. Both patients had a persistent post-transplant daily urine output of 7-8 l/day and continued to have a variable serum creatinine level, dependent on intravenous hydration, more then 3 weeks after transplantation. Bilateral laparoscopic native-kidney nephrectomy in children has previously been reported. However, to the best of our knowledge, laparoscopic nephrectomy has not been described after kidney transplantation and certainly not in the immediate post-transplantation period. The procedure was well tolerated and did not affect renal graft function. In fact, following the procedure, serum creatinine levels stabilized, while daily fluid requirements decreased to 2.5-3.5 l/day in both patients. We concluded that bilateral native-kidney nephrectomy can be safely performed in paediatric renal transplant recipients in the immediate post-transplantation period. This new approach may allow preemptive transplantation and avoid the need for a transition period on dialysis in patients for whom pre-transplant nephrectomy is not absolutely indicated.

The Calgary protocol for bracing of pectus carinatum: a preliminary report

BACKGROUND

The optimal treatment of pectus carinatum (PC) deformities is unclear. We propose a nonoperative approach using a lightweight, patient-controlled dynamic chest-bracing device.

MATERIAL AND METHODS

With ethical approval, 24 patients with PC were treated at the Alberta Children's Hospital between January 1998 and April 2005. There were 6 (25%) females and 18 (75%) males, with a mean age of 12.9 years at the onset of treatment. Treatment involved fitting of a lightweight, patient-controlled chest brace, worn for 23 hours per day (correction phase [CP]) until the convex deformity was corrected. Following correction of the deformity, bracing was reduced to 8 hours per day (maintenance phase) until axial skeletal maturation ceased. Monitoring was done by measurement of the external pectus carinatum protrusion as well as subjective patient and surgeon appraisal of appearance and exercise tolerance.

RESULTS

Nineteen (79.2%) patients have completed initial treatment (mean CP time, 4.3 +/- 2.1 months). There were 3 patients (12.5%) who were noncompliant, and 2 (8.3%) are still in the initial CP phase of therapy. Fourteen (58.3%) patients are presently in maintenance phase, nocturnally braced, and 2 (8.3%) have completed therapy. In patients completing initial treatment, the protrusion pectus carinatum protrusion (pre 22 +/- 6 vs post 6.0 +/- 6.2) and subjective appearance (change + 1.8+/-0.4) showed a significant improvement (P < .001 for both) with no change in exercise tolerance.

CONCLUSION

Compressive bracing results in a significant subjective and objective improvement in PC appearance in skeletally immature patients. However, patient compliance and diligent follow up appear to be paramount for the success of this method of treatment. Further studies are required to show the durability of this method of treatment.

The effects of systemic hypoxia on colon anastomotic healing: an animal model

PURPOSE

Acute postoperative systemic hypoxia occurs frequently in the clinical setting following intestinal resection, as a result of complications such as pneumonia, pulmonary edema, or the acute respiratory distress syndrome. Although it is well established that oxygen is essential for metabolism in general and intestinal anastomotic healing, the mechanisms by which systemic hypoxia affect this process are not clear. The purpose of this study was to establish an animal model to simulate acute systemic hypoxia and to examine the effects on anastomotic healing. We investigated the hypothesis that systemic hypoxia impairs anastomotic healing in the colon by disrupting revascularization via changes in the expression of two putative angiogenic factors: inducible nitric oxide synthase and vascular endothelial growth factor.

METHODS

Phase I: Juvenile male Sprague-Dawley rats underwent carotid artery cannulation. In a controlled environment the FiO2 was incrementally decreased from 21 to 9 percent and the resultant PaO2 measured. Phase II: Animals underwent colonic transection with immediate reanastomosis and were placed in either a normoxic (FiO2 21 percent) or hypoxic (FiO2 11 percent) environment for seven days. Perianastomotic in vivo tissue oxygen saturation was measured before segmental colon resection in each of the animals and at seven days before measurement of anastomotic bursting pressure. Perianastomotic tissue samples were assessed by Western blot assay for the expression of vascular endothelial growth factor and inducible nitric oxide synthase protein. Sections from each tissue sample were taken and evaluated by a pathologist blinded to treatment group for determination of anastomotic healing score.

RESULTS

Phase I: Incrementally decreasing the FiO2 resulted in a progressive decrease in PaO2 (r2 = 0.77). Phase II: Animals maintained in a hypoxic environment had a significant decrease in tissue oxygen saturation (73 +/- 9 percent vs. 94 +/- 3 percent; P < 0.0001) and anastomotic bursting pressure (118 +/- 18 mmHg vs. 207 +/- 30 mmHg; P < 0.0001) compared with normoxic controls. Systemic hypoxia induced a significant increase, when compared with normoxic controls, in vascular endothelial growth factor (247.1 +/- 9.5 vs. 142.2 +/- 10.6; P < 0.0001) and inducible nitric oxide synthase (259.6 +/- 21.1 vs. 120.2 +/- 10.9; P < 0.0001) protein expression and led to a significant decrease in the overall wound-healing score.

CONCLUSION

This study validates a new animal model to study the effects of acute systemic hypoxia on colonic anastomotic healing. In this model, systemic hypoxia directly translated into local tissue hypoxia, and anastomotic healing was impaired. Contrary to our original hypothesis, hypoxia led to a significant increase in vascular endothelial growth factor and inducible nitric oxide synthase protein expression at the colonic anastomotic site. Impairment in anastomotic integrity despite upregulation of these angiogenic factors could be a result of the inability of wounded tissue to respond to vascular endothelial growth factor and inducible nitric oxide synthase or alternatively, hypoxia may adversely affect collagen synthesis and deposition directly.

A pilot study of the use of epidermal growth factor in pediatric short bowel syndrome

BACKGROUND

This study examined the effects of enterally administered epidermal growth factor (EGF) on nutrient absorption and tolerance of enteral feeds in pediatric patients with short bowel syndrome (SBS).

METHODS

Patients identified with severe SBS (<25% bowel length predicted for age) were prospectively enrolled in treatment using human recombinant EGF (1-53); 100 microg/kg per day given mixed with enteral feeds and patients were treated for 6 weeks. End points followed were patient weight, tolerance of enteral feeds, nutrient absorption, and intestinal permeability as determined using carbohydrate probes and hematologic values for liver function parameters.

RESULTS

Five patients were treated with EGF; all showed a significant improvement in carbohydrate absorption (3-0 methylglucose): absorption 24.7% +/- 9.7% pretreatment vs 34.1% +/- 13.8% posttreatment and improved tolerance of enteral feeds (enteral energy as % of total energy, 25% +/- 28% pretreatment vs 36% +/- 24% posttreatment; mean +/- SD; P < .05 by Wilcoxon's signed rank test). Epidermal growth factor treatment was not associated with significant changes in intestinal permeability, the rate of weight gain, or liver function tests. During the treatment phase, no patients developed episodes of sepsis; however, within 2 weeks of discontinuation of EGF treatment, 3 patients developed septic episodes. No adverse effects of EGF administration were noted.

CONCLUSIONS

These results suggest that enteral treatment with EGF in pediatric SBS improves nutrient absorption, increases tolerance with enteral feeds, and may improve the infection rate. Further studies exploring treatment strategies including the timing and duration of EGF administration are indicated.

Midterm evaluation of cardiopulmonary effects of closed repair for pectus excavatum

BACKGROUND/PURPOSE

Since the introduction of the closed technique for repair of pectus excavatum, increasing numbers of patients are presenting for surgery. However, controversy exists regarding the effects of repair on long-term cardiopulmonary outcome. This report details the effects over time of closed repair of pectus excavatum on pulmonary function, cardiac function, exercise tolerance, and the patient's perception of appearance and subjective ability to exercise.

METHODS

All patients undergoing closed repair of pectus excavatum were evaluated prospectively. Preoperative computed tomography scan, static pulmonary function studies, exercise tolerance, and echocardiographic evaluation of cardiac function were done. Studies were repeated at 3 and 21 months post-bar placement, and then 3 months after bar removal.

RESULTS

Pre- and postoperative data were available for an initial 48 patients, with 11 patients completing the full evaluation after bar removal. All measures of pulmonary function including forced expiratory volume in 1 second and forced vital capacity were reduced at 3 months postoperation, with a gradual increase during follow-up; however, pulmonary function remained below normative values for patients without pectus excavatum of similar age. Cardiac function as measured by cardiac output and index was increased at 3 months postoperation and maintained thereafter. Exercise tolerance declined initially and then increased by the 21-month evaluation point and after bar removal. Patients reported a subjective improvement in the ability to exercise immediately after bar insertion.

CONCLUSIONS

These results corroborate previous studies which suggested that after closed repair of pectus excavatum there is an immediate subjective improvement in the ability to exercise which is paralleled by an improvement in cardiac output. However, there is an early postoperative decline in pulmonary function which does improve over time; however, this does not reach normal values for similar weight. Further studies are needed to determine whether these results are maintained, or whether after bar removal there is a further improvement in pulmonary status. These results do support the use of the closed repair of pectus excavatum for maintaining and possibly improving cardiopulmonary function in this patient population.

3-0 methylglucose uptake as a marker of nutrient absorption and bowel length in pediatric patients

BACKGROUND

Inert carbohydrate probes are commonly used to assess intestinal permeability; we have previously shown that the actively transported moiety 3-0 methylglucose (3-0 MG) is a useful marker of intestinal surface area and nutrient absorption in animal models of short bowel syndrome (SBS). This study examines the correlation of 3-0 MG absorption with nutrient absorption, bowel length, and the tolerance of enteral feeds in pediatric patients.

METHODS

Fifteen children (1 month to 15 years in age) were studied after intestinal surgery. All had a stoma, 2 were > 1 year of age, the remainder had surgical intervention as a neonate or within the first month of life. Eight had SBS (50% expected bowel length for age). Bowel length was measured intraoperatively. Nutrient absorption was quantified with a 48-hour bowel study, measuring fat, protein, and carbohydrate output directly. 3-0 MG absorption and intestinal permeability were quantified using a solution containing 30 mg/mL 3-0 MG, 20 mg/mL mannitol and 30 mg/mL lactulose (osmolarity 352, given at 1 mL/kg via feeding tube). Subsequent urine production was collected for 8 hours, and probe recovery measured using HPLC.

RESULTS

3-0 MG absorption was significantly correlated with nutrient absorption. The correlation with protein absorption was r2 = .59, fat r2 = .62 and carbohydrate r2 = .56. The correlation between 3-0 MG absorption and bowel length was r2 = .58. 3-0 MG absorption was significantly lower in SBS patients vs patients with normal bowel length (15.8 +/- 6.7 vs 30.5 +/- 10.2%). 3-0 MG absorption also correlated with the ability to tolerate enteral feeds (r2 = .38; p < .03 for all comparisons).

CONCLUSIONS

3-0 MG may be a useful marker of nutrient absorption and bowel length in pediatric patients with short bowel syndrome. The simplicity and reproducibility of the method make it an attractive option for following patient outcomes. Further studies are suggested to determine the utility of these markers in directing the clinical management of patients.

Nutrient-stimulated GLP-2 release and crypt cell proliferation in experimental short bowel syndrome

Glucagon-like peptide-2 (GLP-2) is an enteroendocrine peptide that is released in response to luminal nutrients and has unique trophic actions in the gastrointestinal tract. These features suggest GLP-2 may be important in controlling intestinal adaptation. We examined the relationship over time of GLP-2 production and adaptation to intestinal resection, the effects of resection-induced malabsorption on GLP-2 production, and the correlation of endogenous serum GLP-2 levels with adaptation as measured by crypt-cell proliferation (CCP). We initially examined the effect of nutrient malabsorption, induced by a 90% resection of the proximal intestine studied on day 4, on the time course and levels of GLP-2 release. Secondly, the degree of malabsorption was varied by performing intestinal transection or 50, 75, or 90% resection of proximal small intestine. Finally, the relationship of GLP-2 levels over time with adaptation to a 90% resection was examined by determining GLP-2 levels on days 7, 14, and 28, and correlating this with intestinal adaptation, as assessed by morphology and CCP rate. A 90% resection significantly increased basal and postprandial GLP-2 levels, with a net increase in nutrient-stimulated exposure over 90 min; GLP-2 exposure (integrated levels vs. time) increased 12.7-fold in resected animals (P < 0.001). Basal and postprandial GLP-2 levels significantly correlated with the magnitude of intestinal resection (r(2) = 0.71; P < 0.001), CCP (r(2) = 0.48; P < 0.005), and nutrient malabsorption (protein, P < 0.001; fat, P < 0.005). The increase in CCP was maintained to 28 days after small bowel resection and was associated with an ongoing elevation in GLP-2 release. These findings suggest that GLP-2 is important in initiating and maintaining the small intestinal adaptive response to resection.