Decrease in hepatic circulation induces hepatic fibrosis in a neonatal piglet model with short bowel syndrome

Significance of the Extent of Intestinal Resection on the Outcome of a Short-bowel Syndrome in a Porcine Model

AIM OF THE STUDY

Insufficient data are available to determine the most suitable extent of intestinal resection required to induce short-bowel syndrome (SBS) in pigs. This study aimed to compare the three main SBS-models published.

METHODS

A 75%, 90%, or 100% mid-intestinal resection was performed in groups of n = 5 pigs each. Clinical (body weight, stool consistency) and biochemical (serum eletrolytes, citrulline, albumin, prealbumin, and transferrin) parameters were determined daily, functional (D-xylose resorption) and histological (intestinal villus length) parameters were determined after 2 weeks. A t-test and ANOVA were used for statistical analysis.

RESULTS

Only in the 100% group, we observed a persistent weight loss (13.6 ± 3.8%) and diarrhea, as well as a decrease in prealbumin-levels (41%) and transferrin levels (33%). Serum electrolytes remained stable in all groups during the observation period. Citrulline stabilized at different levels (100% group 13.9 ± 1.0 μmol/L; 90% group 18.8 ± 1.0 μmol/L; 75% group 26.3 ± 1.4 μmol/L; all p < .05). D-xylose resorption was lowest in the 100%, followed by 90% and 75% group (100% group 32.8 ± 4.9 mg/L; 90% group 50.0 ± 19.6 mg/L; 75% group 57.8 ± 8.8 mg/L; p = .393). Intestinal villus length decreased in all groups (100% group 11.0%; 90% group 14.0%; 75% group 19.1%).

CONCLUSIONS

75% intestinal resection is less suitable as an SBS model, as animals tend to recover remarkably. The 90% model is suitable for longer-term studies, as animals might survive longer due to partial compensation. Due to severe nutritional, biochemical, and physiological derangements, the 100% model can only be used for acute experiments and those immediately followed by small bowel transplantation.

Massive bowel resection upregulates the intestinal mRNA expression levels of cellular retinol-binding protein II and apolipoprotein A-IV and alters the intestinal vitamin A status in rats

Short bowel (SB) syndrome causes the malabsorption of various nutrients. Among these, vitamin A is important for a number of physiological activities. Vitamin A is absorbed by epithelial cells of the small intestine and is discharged into the lymphatic vessels as a component of chylomicrons and is delivered to the liver. In the present study, we used a rat model of SB syndrome in order to assess its effects on the expression of genes associated with the absorption, transport and metabolism of vitamin A. In the rats with SB, the intestinal mRNA expression levels of cellular retinol-binding protein II (CRBP II, gene symbol Rbp2) and apolipoprotein A-IV (gene symbol Apoa4) were higher than those in the sham-operated rats, as shown by RT-qPCR. Immunohistochemical analysis revealed that absorptive epithelial cells stained positive for both CRBP II and lecithin retinol acyltransferase, which are both required for the effective esterification of vitamin A. In the rats with SB, the retinol content in the ileum and the retinyl ester content in the jejunum were lower than those in the sham-operated rats, as shown by quantitative analysis of retinol and retinyl esters by high performance liquid chromatography. These results suggest that the elevated mRNA expression levels of Rbp2 and Apoa4 in the rats with SB contribute to the effective esterification and transport of vitamin A.

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.

Intestinal proteomics in pig models of necrotising enterocolitis, short bowel syndrome and intrauterine growth restriction

Necrotising enterocolitis (NEC), short bowel syndrome (SBS) and intrauterine growth restriction (IUGR) are three conditions associated with intestinal dysfunction in newborn infants, particularly those born preterm. Piglet (Sus scrofa) models have recently been developed for NEC, SBS and IUGR, and tissue proteomic analyses have identified unknown pathways and new prognostic disease markers. Intestinal HSPs, iron metabolism proteins and proteins related to amino acid (e.g. arginine) and glucose metabolism are consistently affected by NEC progression and some of these proteins are also affected by SBS and IUGR. Parallel changes in some plasma and urinary proteins (e.g. haptoglobin, globulins, complement proteins, fatty acid binding proteins) may mirror the intestinal responses and pave the way to biomarker discovery. Explorative non-targeted proteomics provides ideas about the cellular pathways involved in intestinal adaptation during the critical neonatal period. Proteomics, combined with other -omic techniques, helps to get a more holistic picture of intestinal adaptation during NEC, SBS and IUGR. Explorative -omic research methods also have limitations and cannot replace, but only supplement, classical hypothesis-driven research that investigate disease mechanisms using a single or few endpoints.

Novel neonatal piglet models of surgical short bowel syndrome with intestinal failure

OBJECTIVES

Short bowel syndrome occurring after surgery for acquired or congenital intestinal abnormalities causes considerable neonatal morbidity and mortality. Animal models are a valuable research tool for this problem; however, few successful neonatal models have been developed and most do not include distal intestinal resection as seen commonly in human babies. We report novel piglet models addressing these gaps.

SUBJECTS AND METHODS

Neonatal piglets (1-6 days) underwent venous and gastric catheter insertion and 75% intestinal resection. Group 1 (n = 6) had midintestinal resection with jejunoileal anastomosis; group 2 (n = 5) had distal intestinal resection with jejunocolic anastomosis; group 3 (n = 5) were sham controls; and group 4 (n = 5) were sow reared. Postoperatively, groups 1 to 3 piglets commenced parenteral nutrition (PN), and enteral nutrition was introduced and advanced using a standard regimen. Data collection included days on PN, weight gain, fat absorption, small intestine lengthening, and bowel/liver histology.

RESULTS

Group 2 piglets had more days on PN (P = 0.008), less weight gain (P = 0.027), and greater malabsorption (P = 0.012). They did not show small intestine lengthening and had more cholestatic liver disease. Group 1 piglets had histological evident intestinal adaptation and 1.5-fold intestinal lengthening (P = 0.001).

CONCLUSIONS

These novel piglet models of short bowel syndrome are the first to represent the full clinical spectrum of intestinal failure as observed in human neonates. By considering the impact of different short bowel anatomy on potential for adaptation and growth, these animal models are a significant advance. They permit evaluation of new therapies to promote intestinal adaptation and reduce complications, such as cholestasis.