Pamela R. Wizzard

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.

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.

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.

Parenteral Soy Oil and Fish Oil Emulsions: Impact of Dose Restriction on Bile Flow and Brain Size of Parenteral Nutrition-Fed Neonatal Piglets.

BACKGROUND Parenteral nutrition (PN)-associated liver disease (PNALD) remains a significant cause of morbidity and mortality for neonates dependent on PN. Total fat emulsion dose and composition, particularly the large amount of ω-6 long-chain polyunsaturated fatty acids in plant oils, have been proposed as risk factors for PNALD. We hypothesized restriction of the dose of emulsion would prevent PNALD, regardless of the composition, but growth could be compromised. METHODS Using a neonatal piglet model, we compared conventional soy oil emulsion (Intralipid), dosed high (SO10, n = 8: 10 g/kg/d) and low (SO5, n = 6: 5 g/kg/d), with fish oil (Omegaven), dosed low (FO5, n = 8: 5 g/kg/d). Piglets were given isonitrogenous PN for 14 days. The normal range for all parameters was determined by measurement in equivalent aged sow-reared piglets. RESULTS Bile flow was lower with high-dose Intralipid, outside the normal range, while higher for the other groups (SO10, 5.4 µg/g; SO5, 8.6 µg/g; FO5, 13.4 µg/g; P = .010; normal range, 6.5-12.2 µg/g). Total body weight was low in all treatment groups (SO10, 4.4 kg; SO5, 4.5 kg; FO5, 5.0 kg; P = .038; normal range, 5.2-7.3 kg). Brain weight was not different between groups (SO10, 40.3 g; SO5, 36.0 g; FO5, 36.6 g; P = .122; normal range, 41.8-51.4 g). Corrected for body weight, brain weight was lowest in the fish oil group (SO10, 9.3 g/kg; SO5, 8.0 g/kg; FO5, 7.3 g/kg; P < .001; normal range, 5.9-9.0 g/kg). CONCLUSION Low-dose fat emulsions reduce the risk of developing PNALD. Further investigation of the risk to brain development in neonates exposed to dose restriction, particularly with fish oil, is required.

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.

Liver Disease, Systemic Inflammation, and Growth Using a Mixed Parenteral Lipid Emulsion, Containing Soybean Oil, Fish Oil, and Medium Chain Triglycerides, Compared With Soybean Oil in Parenteral Nutrition–Fed Neonatal Piglets

BACKGROUND The optimal parenteral lipid emulsion for neonates should reduce the risk of intestinal failure-associated liver disease and inflammation, while supporting growth and development. This could be best achieved by balanced content of ω-6 and ω-3 polyunsaturated fatty acids (PUFAs). Using a neonatal piglet model of parenteral nutrition (PN), we compared a 100% soy oil-based emulsion (ω-6:ω-3 PUFA: 7:1) with a mixed lipid emulsion comprising 30% soy oil, 30% medium-chain triglycerides, 25% olive oil, and 15% fish oil (ω-6:ω-3 PUFA: approximately 2.5:1) with regard to liver disease, inflammation, and fatty acid content in plasma and brain. METHOD Neonatal piglets, 3-6 days old, underwent jugular catheter insertion for isonitrogenous, isocaloric PN delivery over 14 days. The IL group (n = 8) was treated with Intralipid; the ML group (n = 10) was treated with the mixed lipid (SMOFlipid). Bile flow, liver chemistry, C-reactive protein (CRP), and PUFA content in plasma phospholipids and brain were compared. RESULTS Compared with the IL group, ML-treated piglets had increased bile flow (P = .008) and lower total bilirubin (P = .001) and CRP (P = .023) concentrations. The ω-6 long-chain PUFA content was lower in plasma and brain for the ML group. The key ω-3 long-chain PUFA for neonatal development, docosahexaenoic acid (DHA), was not different between groups. CONCLUSION The mixed lipid, having less ω-6 PUFA and more ω-3 PUFA, was able to prevent liver disease and reduce systemic inflammation in PN-fed neonatal piglets. However, this lipid did not increase plasma or brain DHA status, which would be desirable for neonatal developmental outcomes.

Role of glucagon-like peptide-2 deficiency in neonatal short-bowel syndrome using neonatal piglets

Background:Short-bowel syndrome (SBS) is the most common cause of neonatal intestinal failure. Recovery requires intestinal adaptation, dependent on enteral nutrition (EN) and growth factors such as glucagon-like peptide–2 (GLP-2), which is secreted from L cells in the ileum. Neonatal SBS often results in loss of ileum; therefore, we hypothesized that without ileum, endogenous GLP-2 production would be inadequate to promote adaptation. We compared endogenous GLP-2 production and adaptation in neonatal animals with SBS, with and without ileum.Methods:Neonatal piglets (4–6 d) were randomized to 75% mid-intestinal resection, 75% distal-intestinal resection, or sham control without resection. Postoperatively, all piglets commenced parenteral nutrition (PN), tapering as EN was increased to maintain specific growth.Results:The resected SBS piglets developed intestinal failure, requiring a longer duration of PN support and experiencing fat malabsorption. The piglets without ileum were not able to wean from PN during the study and did not show adaptation, specifically growth in intestinal length or crypt hyperplasia on histology of the jejunum. Adaptation was observed in the resected SBS piglets with ileum, and these piglets also had an increased plasma GLP-2 level that was not observed in piglets without ileum.Conclusion:SBS piglets with ileum undergo adaptation associated with increased endogenous GLP-2 production. SBS piglets without ileum undergo limited adaptation and severe intestinal failure, requiring prolonged PN support. This appears to be related to a deficiency in endogenous GLP-2 production.

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.

Platelet Arachidonic Acid Deficiency May Contribute to Abnormal Platelet Function During Parenteral Fish Oil Monotherapy in a Piglet Model

BACKGROUND Fish oil monotherapy has been an advance for treating intestinal failure-associated liver disease (IFALD). However, such patients are at risk of bleeding complications from liver disease and because fish oil can inhibit thrombosis. We have previously reported abnormal platelet function in neonatal piglets given fish oil monotherapy during parenteral nutrition (PN). The purpose of this study was to determine if abnormal fatty acid composition of the platelets could explain the prior observed antiplatelet effect. METHODS Neonatal piglets were assigned to 2 treatments: PN with fish oil monotherapy (FO; n = 4) or PN with soy oil (SO; n = 5). On day 14, plasma was collected and platelets isolated by centrifuging. The fatty acid content in plasma and platelet plug were measured using gas liquid chromatography and compared with controls (CON; n = 5). RESULTS The arachidonic acid (AA) content in the FO group was on average half that of the SO group, in both the platelets (FO, 3.5% vs SO, 7.6%; P = .021; CON, 4.5%-11%) and the plasma (FO, 3.8% vs SO, 9.2%; P = .002; CON, 6.1%-9.5%). No bleeding complications were observed for any piglets during PN treatment. CONCLUSIONS Using platelet mapping, we have previously shown that neonatal piglets given fish oil monotherapy have abnormal platelet function in the AA pathway. This report demonstrates that such an abnormality can be explained by platelet AA deficiency. Platelet mapping and platelet fatty acid analysis should be undertaken in human infants treated with fish oil monotherapy during PN.

Lipid Emulsion Formulation of Parenteral Nutrition Affects Intestinal Microbiota and Host Responses in Neonatal Piglets

Background: Total parenteral nutrition (TPN) is a cause of intestinal microbial dysbiosis and impaired gut barrier function. This may contribute to life-threatening parenteral nutrition–associated liver disease and sepsis in infants. We compared the effects of a lipid emulsion containing long-chain &ohgr;-3 polyunsaturated fatty acids (PUFAs; SMOFlipid) and a predominantly &ohgr;-6 PUFA emulsion (Intralipid) on microbial composition and host response at the mucosal surface. Materials and Methods: Neonatal piglets were provided isocaloric, isonitrogenous TPN for 14 days versus sow-fed (SF) controls. Equivalent lipid doses (10 g/kg/d) were given of either SMOFlipid (ML; n = 10) or Intralipid (SO; n = 9). Ileal segments and mucosal scrapings were used to characterize microbial composition by 16S rRNA gene sequencing and quantitative gene expression of tight junction proteins, mucins, antimicrobial peptides, and inflammatory cytokines. Results: The microbial composition of TPN piglets differed from SF, while ML and SO differed from each other (analysis of molecular variance; P < .05); ML piglets were more similar to SF, as indicated by UniFrac distance (P < .05). SO piglets showed a specific and dramatic increase in Parabacteroides (P < .05), while ML showed an increase in Enterobacteriaceae (P < .05). Gene expression of mucin, claudin 1, &bgr;-defensin 2, and interleukin 8 were higher in TPN; overall increases were significantly less in ML versus SO (P < .05). Conclusion: The formulation of parenteral lipid is associated with differences in the gut microbiota and host response of TPN-fed neonatal piglets. Inclusion of &ohgr;-3 long-chain PUFAs appears to improve host-microbial interactions at the mucosal surface, although mechanisms are yet to be defined.