Trophic peptide therapies for neonatal short bowel syndrome: actions and mechanisms studied in a preclinical model

• Author / Creator

  Lim, David W

• Short bowel syndrome (SBS) occurs when a significant length of intestine is surgically resected for both congenital and acquired intestinal abnormalities and remains a significant cause of morbidity and mortality in neonates. With an insufficient amount of intestine available for nutrient absorption, neonates with SBS are dependent on parenteral nutrition (PN) for survival but many continue to develop and succumb to PN-associated complications such liver disease and sepsis. In order for these children to survive, the remnant intestine must adapt and improve nutrient absorption over time. Glucagon-like peptide-2 (GLP-2) is a distal intestinal-derived peptide that is trophic to the intestine and stimulates intestinal adaptation after major resection. Diseases that lead to SBS in neonates, such as necrotizing enterocolitis, most commonly affect and require removal of the distal intestine, including ileum. Thus, GLP-2 may be the limiting factor for adaptation in human neonates with SBS. Furthermore, the intestinotrophic effects of GLP-2 may be augmented by the simultaneous delivery of either enteral nutrition (EN) or epidermal growth factor (EGF). We thus hypothesized that GLP-2 therapy stimulates intestinal growth and function in neonatal SBS, and that the intestinotrophic effects of GLP-2 are augmented when given in combination with either EN or EGF therapy. For these studies, neonatal piglets were block-randomized to either a 75% mid-intestinal resection (JI model) with jejunoileal anastomosis (leaving equal lengths of jejunum and ileum) or 75% distal-intestinal resection (JC model) (removing all ileum) with jejunocolic anastomosis or sham (no resection) control. Piglets also received a jugular venous catheter and a gastrostomy tube for the provision of PN and EN, respectively. Piglets were subsequently maintained for 7 days. In the first study, piglets received either intravenous GLP-2 (42 μg/kg/day) or saline control and either remained on total PN (0% EN) or received EN at 40% of nutritional requirement. In the second study, piglets received saline control, intravenous GLP-2 (42 μg /kg/day), enteral EGF (80 µg/kg/day), or combined GLP-2 and EGF and all piglets received EN at 20% of nutritional requirement. Structural adaptation was assessed by the change in intestinal length, mucosal and intestinal weight, and histopathology. Functional adaptation was assessed by measuring several parameters: the relative gene expression of nutrient transporters, digestive enzymes and tight junction proteins, measurement of intestinal permeability using the Üssing chamber apparatus, fat absorption and weight gain. In the first study, we observed that in piglets maintained on total PN in the absence of treatment, the JI model demonstrated intrinsic structural adaptation, including increased intestinal weight and villus height, while the JC model did not. In this group that was not enterally fed, GLP-2 treatment induced histological adaptation in the JC model. In contrast, enteral feeding at 40% of nutritional requirement resulted in intestinal lengthening and increased intestinal weight in the JI model, while increased diarrhea and decreased weight gain were observed in the JC model. GLP-2 treatment in this fed group of piglets had no effect in the JI model but increased villus height in the JC model. We did not observe differences in the gene expression of nutrient transporters or tight junction proteins. In the second study, combined EGF and GLP-2 treatment increased intestinal length by 15%, regardless of surgical anatomy. Both GLP-2 alone and combination therapy increased intestinal weight in the JC model, and jejunal mucosal weight and villus height in both JI and JC models. Combination therapy decreased intestinal permeability to both mannitol and polyethylene glycol in both surgical models. There was no difference in fat absorption or weight gain. Our results demonstrate the beneficial effects of exogenous GLP-2 treatment in the JC model, which anatomically represents most human infants with SBS. In contrast, the JI model demonstrated greater structural adaptation in response to enteral feeding. We further demonstrated a beneficial effect of combined GLP-2 and EGF treatment on increasing intestinal length and absorptive surface area in both models, which may lead to improved nutrient absorption. The benefit of decreased intestinal permeability with combination therapy translates to strengthened barrier function and decreased risk for bacterial translocation. GLP-2 therapy may thus benefit human infants with SBS, who commonly experience small intestinal bacterial overgrowth. Moving forward, our studies provide important preclinical data with regards to the translation of trophic peptide therapies in neonatal SBS.

• Subjects / Keywords

  • Short bowel syndrome
  • Intestinal adaptation
  • Epidermal growth factor
  • Neonatal
  • Glucagon-like peptide-2
  • Intestinal failure

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3CN6Z719

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.