Intestinal resection affects whole-body arginine synthesis in neonatal piglets.

BACKGROUND: Previous studies in piglets show a direct relationship between intestinal mass and arginine (Arg) synthesis. We aimed to study the effects of 75% intestinal resection on whole-body Arg synthesis. METHODS: Piglets were allocated to sham or jejunocolic (JC) surgery and to enteral nutrition (EN) at 20% [sham (n = 8), JC (n = 10)], or 40% [sham (n = 4), JC (n = 5)]. A gastric tube was placed for EN and a venous catheter for parenteral nutrition and blood sampling. On day 6, a primed bolus and constant infusion of Arg m + 2 label and proline m + 1 label was delivered. In addition, 40% EN piglets received a citrulline (Cit) m + 3 tracer. Blood sampling was undertaken and whole-body Arg synthesis was calculated. On day 7, intestinal length was measured, and samples were collected for gene expression (PCR quantification) and histopathology. RESULTS: On Day 7, sham piglets showed intestinal lengthening compared to JC (p = 0.02). Whole-body Arg synthesis was similar between groups (p = 0.50). Adjusting for absolute small intestinal length, JC piglets had greater Arg synthesis (p = 0.01). Expression of arginosuccinase was upregulated in the jejunum of JC compared to sham on 20% EN (p = 0.03). CONCLUSION: This demonstrates for the first-time adaptive changes in intestinal Arg synthesis following intestinal resection. IMPACT: The intestine makes a critical contribution to whole-body arginine synthesis, particularly in neonates, a human population at risk for short bowel syndrome. Therefore, we studied intestinal arginine synthesis in a neonatal piglet model of short bowel syndrome and demonstrated adaptive changes in the intestine that may preserve whole-body arginine synthesis, despite loss of intestinal mass. This research adds new information to our understanding of the effects a massive intestinal resection has on amino acid metabolism during neonatal development.

Mixed Lipid, Fish Oil, and Soybean Oil Parenteral Lipids Impact Cholestasis, Hepatic Phytosterol, and Lipid Composition.

OBJECTIVES: In parenteral nutrition-dependent infants and children, intestinal failure (IF)-associated liver disease (IFALD) remains an important problem. A comparative study was undertaken of parenteral mixed lipid (ML), ω-3 predominant fish oil (FO), and ω-6 predominant soybean oil (SO) emulsions in regards to hepatic phytosterol, neutral lipid, fatty acid (FA) content, and the relationship to cholestasis in piglets. METHODS: Neonatal piglets received parenteral nutrition, varying in lipid dose (5 or 10 g·â€Škg ·â€Šday) and formulation: SO5 (n = 5), SO10 (n = 5), FO5 (n = 5), and ML10 (n = 5). On day 14, liver chemistry, bile flow, histology and neutral lipid staining were assessed. Hepatic triglyceride FA content was determined using thin layer and gas chromatography, and phytosterol content was assessed using gas chromatography-mass spectrometry. RESULTS: SO groups had higher prevalence of biochemical cholestasis (P < 0.04) and lower bile flow (P < 0.0001). Hepatic campesterol, stigmasterol, and ß-sitosterol were highest in SO10 (P < 0.0001). Hepatic FA (P < 0.03) and ω-6/ω-3 FA ratio (P < 0.0001) were higher in the SO groups. Neutral lipid accumulation (P = 0.3) and liver histology (P = 0.16) were not different between groups. Univariate predictors of bile flow were: campesterol (r = -0.77, P = 0.001), ß-sitosterol (r = -0.74, P = 0.002), stigmasterol (r = -0.74, P = 0.002), ω-6 FA (r = -0.72, P = 0.002), and ω-3 FA (r = 0.59, P = 0.02). Only campesterol independently predicted bile flow. CONCLUSIONS: ML and FO lipid emulsions reduce cholestasis in association with lowered hepatic phytosterol and lipid content. Lower hepatic phytosterol and ω-6 FA content, and higher ω-3 FA content are hepatoprotective. Multivariate analysis suggests reduced phytosterol accumulation may best explain the hepatoprotective effect of fish oil-containing lipids.

Plasma citrulline is not a biomarker for intestinal adaptation in short bowel syndrome, studied in piglets: a model for human neonates.

BACKGROUND: There are no in vivo methods to measure adaptation in neonatal short bowel syndrome (SBS). We evaluated citrulline (Cit) levels in neonatal piglet surgical models of SBS. METHODS: Piglets underwent 75% mid-intestinal resection with jejunoileal anastomosis (JI), 75% distal resection of ileum with jejunocolic anastomosis (JC) or sham surgery. Jugular and gastric catheters were inserted for parenteral and enteral nutrition. On D7, small intestine length and weight were measured, jejunum collected for histopathology and Cit level determined. RESULTS: JI (n = 5) compared to JC (n = 5) had increased small intestinal length (JC - 17.5 cm; JI +22.0 cm; p = 0.02) and mass (JC 43.1 mg/cm/kg; JI 51.3 mg/cm/kg; p = 0.02), while Cit did not differ (JI 801.0 µM; JC 677.7 µM; p = 0.90). Including non-resected shams (n = 4), Cit correlated with length (R2 = 0.48; p = 0.006), but not for SBS alone (R2 = 0.11; p = 0.4), mass (R2 = 0.05; p = 0.5). A second experiment compared change in Cit levels from baseline to D7. Levels declined in sham (n = 8) and JC (n = 10) (sham - 110.1 µM; JC - 56.6 µM; p = 0.17), regardless of intestinal lengthening (sham 29.9 cm; JC - 10.4 cm; p = 0.002). CONCLUSION: Citrulline levels predict large differences in intestinal length and 'identify' SBS. However, citrulline cannot discriminate between adaptation in JI and JC, nor predict intestinal lengthening.

Synergy of glucagon-like peptide-2 and epidermal growth factor coadministration on intestinal adaptation in neonatal piglets with short bowel syndrome.

Glucagon-like peptide-2 (GLP-2) and epidermal growth factor (EGF) treatment enhance intestinal adaptation. To determine whether these growth factors exert synergistic effects on intestinal growth and function, GLP-2 and EGF-containing media (EGF-cm) were administered, alone and in combination, in neonatal piglet models of short bowel syndrome (SBS). Neonatal Landrace-Large White piglets were block randomized to 75% midintestinal [jejunoileal (JI) group] or distal intestinal [jejunocolic (JC) group] resection or sham control, with 7-day infusion of saline (control), intravenous human GLP-2 (11 nmol·kg-1·day-1) alone, enteral EGF-cm (80 µg·kg-1·day-1) alone, or GLP-2 and EGF-cm in combination. Adaptation was assessed by intestinal length, histopathology, Üssing chamber analysis, and real-time quantitative PCR of intestinal growth factors. Combined EGF-cm and GLP-2 treatment increased intestinal length in all three surgical models (P < 0.01). EGF-cm alone selectively increased bowel weight per length and jejunal villus height in the JI group only. The JC group demonstrated increased intestinal weight and villus height (P < 0.01) when given either GLP-2 alone or in combination with EGF-cm, with no effect of EGF-cm alone. Jejunal permeability of mannitol and polyethylene glycol decreased with combination therapy in both SBS groups (P < 0.05). No difference was observed in fat absorption or body weight gain. IGF-1 mRNA was differentially expressed in JI vs. JC piglets with treatment. Combined treatment with GLP-2 and EGF-cm induced intestinal lengthening and decreased permeability, in addition to the trophic effects of GLP-2 alone. Our findings demonstrate the benefits of novel combination GLP-2 and EGF treatment for neonatal SBS, especially in the JC model representing most human infants with SBS.NEW & NOTEWORTHY Glucagon-like peptide-2 (GLP-2) and epidermal growth factor (EGF) are intestinotrophic, with demonstrated benefit in both animal models and human studies of short bowel syndrome (SBS). The current research shows that over and above known trophic effects, the combination of GLP-2 and EGF synergistically lengthens the bowel in neonatal piglet models of SBS. Most notable benefit occurred with resection of the terminal ileum, the common clinical anatomy seen in neonatal SBS and associated with least de novo lengthening postsurgery.

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.

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.

In parenteral nutrition-fed piglets, fatty acids vary by lipid emulsion and tissue sampled.

BACKGROUND: Children with intestinal failure without liver disease may be given soy-based lipid emulsion (SLE) or mixed lipid emulsion (MLE; containing soy, medium-chain triglyceride, olive, and/or fish oils). Both differ in essential fatty acid content: MLE has added arachidonic acid (AA) and docosahexaenoic acid (DHA). The aim of this study, in neonatal piglets, was to compare serum and tissue fatty acid composition when the emulsions were given at unrestricted doses. METHODS: We compared SLE (n = 15) and MLE (n = 15) at doses of 10-15 g/kg/day in parenteral nutrition (PN). On day 14 we collected serum and tissues. Using gas-liquid chromatography, percentage fatty acids were measured in serum, brain, and liver phospholipid. Comparisons were made to reference values from litter-matched controls (n = 8). RESULTS: Comparing median values, linoleic acid (LA) was lower for MLE vs SLE in serum (-27%), liver (-45%), and brain (-33%) (P < 0.001). AA was lower for MLE in serum (-25%), liver (-40%), and brain (-10%). DHA was higher for MLE in serum (+50%), liver (+200%), and brain (+10%). AA levels were lower for MLE vs control piglets in serum (-81%), liver (-63%), and brain (-9%). DHA levels were higher in serum (+41%), liver (+38%), and brain (+19%). CONCLUSION: This study in piglets has shown that, at unrestricted doses, MLE treatment is associated with low serum and tissue AA compared with SLE and healthy litter-matched controls. Although not yet proven, low tissue AA levels may have functional consequences, and these data support current practice avoiding MLE dose restriction.

Hepatic ultrastructure in a neonatal piglet model of intestinal failure-associated liver disease (IFALD).

This study was designed to evaluate liver disease in neonatal piglets with surgical short bowel syndrome causing intestinal failure with partial parenteral nutrition dependence. The short bowel piglets had 75% surgical resection of distal small intestine, including all ileum and cecum, and were compared with sham controls, without resection, and to healthy sow-reared controls. After 18 days of combined parenteral and enteral nutrition in short bowel and sham piglets, liver tissue was collected for quantitative and semi-quantitative histological and ultrastructural evaluation. The short bowel piglets developed biochemical and histological cholestasis, not observed in sham and control piglets. Ultrastructural examination revealed bile canaliculus dilation with bile plugging, microvillus flattening and disappearance, but without abnormalities of the pericanalicular zone. Interestingly, these data are similar to bile canaliculus changes seen in human neonates with IFALD supporting an initial consideration of this model to elucidate the pathogenesis of IFALD.

The effect of fecal microbial transplant on intestinal microbial composition in short-bowel neonatal piglets.

BACKGROUND: Short-bowel syndrome (SBS) in neonates is associated with microbial dysbiosis due to intestinal surgery, prolonged hospitalization, enteral nutrition, and repeated antibiotic exposure. Sepsis and liver disease, leading causes of morbidity and mortality in SBS, may relate to such intestinal dysbiosis. We investigated the safety and feasibility of fecal microbial transplant (FMT) to alter intestinal microbial composition in SBS piglets. METHODS: Following a 75% distal small-intestinal resection, piglets were fed parenteral nutrition with an elemental diet and randomized to saline (SAL; n = 12) or FMT (n = 12) treatments delivered by gastric tube on day 2 (d2). The FMT donor was a healthy adult pig. Comparisons were also made to healthy sow-fed littermate controls (SOW; n = 6). Stool samples were collected daily, and tissue samples were collected at baseline and termination. Microbial DNA was extracted from stool and analyzed using 16S ribosomal RNA sequencing. RESULTS: All piglets survived to the end point. On d2-d4, FMT piglets had some differences in microbiota composition compared with SAL, SOW, and donor counterparts. Between base and term, there were transitory changes to alpha and beta diversity in FMT and SAL. CONCLUSION: FMT treatment in postsurgical neonatal piglets with SBS appears safe, with no increase in sepsis and no mortality. In SBS piglets, FMT induced transient changes to the intestinal microbiota. However, these changes did not persist long-term.

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.

Mycotic encephalitis, sinus osteomyelitis, and guttural pouch mycosis in a 3-year-old Arabian colt.

Mycotic encephalitis caused severe ataxia and other neurologic deficits in a horse. The finding of a single, large focus of cerebral malacia, with histopathologic evidence of fungal elements, suggested infection was a result of direct transfer from the frontal sinuses, rather than hematogenous spread from the guttural pouch.

Comparing the Intestinotrophic Effects of 2 Glucagon-Like Peptide-2 Analogues in the Treatment of Short-Bowel Syndrome in Neonatal Piglets.

BACKGROUND: In treating short-bowel syndrome (SBS), autonomy from parenteral nutrition (PN) relies upon intestinal adaptation, which can be augmented by glucagon-like peptide-2 (GLP-2) analogues. In neonatal piglets with SBS, we compared intestinal adaptation following treatment with 2 GLP-2 analogues: teduglutide (TED) and apraglutide (APRA) METHODS: Following 75% distal small-intestinal resection, piglets were allocated to 4 treatment groups: saline (CON: n = 8), twice weekly APRA (5 mg/kg/dose; n = 8), and TED once daily (TED, 0.05 mg/kg/dose; n = 8) or twice daily (TEDBID, 0.05 mg/kg/dose; n = 7). Pharmacokinetic (PK) studies were undertaken, and on day 7, small-intestinal length and weight were measured and jejunal tissue collected for histology. RESULTS: PK profiles were different between the 2 analogues. To achieve a comparable exposure to APRA, TED requires twice daily injection (TEDBID). Compared with CON, APRA and TEDBID increased small-bowel length (cm) (CON: 141, APRA: 166, TED: 153, TEDBID: 165; P = .004), whereas APRA increased small-bowel weight (g) (CON: 26, APRA: 33, TED: 28, TEDBID: 31; P = .007) and villus height (mm) (CON: 0.59, APRA: 0.90, TED: 0.58, TEDBID: 0.74; P < .001). CONCLUSION: APRA injected only twice during the 7 consecutive days demonstrated a superior intestinotrophic effect compared with TED injected once daily. Even at more comparable drug exposure, when TED was injected twice a day, APRA showed superior trophic activity at the mucosal level. This is highly relevant for the treatment of pediatric SBS, given the markedly lower dose frequency by subcutaneous injection of APRA.

Durability of Linear Small-Intestinal Growth Following Treatment Discontinuation of Long-Acting Glucagon-Like Peptide 2 (GLP-2) Analogues.

BACKGROUND: Short-bowel syndrome is the leading cause of pediatric intestinal failure, resulting in dependency on long-term parenteral nutrition (PN). To promote enteral autonomy in neonates, a key outcome may be intestinal growth in length. The purpose of this study was to determine if intestinal lengthening persists following discontinuation of treatment with 1 of 2 GLP-2 analogues with different pharmacokinetic profiles. METHODS: Neonatal short-bowel piglets were assigned to saline control (S), 7-day treatment with teduglutide (T) (0.05 mg/kg twice daily), or 7-day treatment with apraglutide (A) (5 mg/kg twice weekly). Comparisons were made between day 7 and day 14 endpoints using analysis of variance. Data included small-intestine length, weight, histology, and quantitative polymerase chain reaction analysis of mucosal transcripts for peptide growth factors and their receptors, nutrient transporters, and tight-junction proteins. RESULTS: Compared with control, 7 days of GLP-2 analogue treatment induced mucosal adaptation based on villus hyperplasia (P = .003), which was not durable 7 days after treatment cessation (day 14; P = .081). Treatment increased intestinal growth in length by day 7 (P = .005), which was maintained (by T) or further increased (by A) at day 14 (P < .001). No significant differences in mucosal transcripts were detected. CONCLUSION: Unlike mucosal adaptation, intestinal growth appears to be a lasting outcome of treatment with long-acting GLP-2 analogues in a neonatal piglet short-bowel model. This has significant clinical implications for neonates, given their potential for intestinal growth. Intestinal lengthening varies between analogues with different half-lives; however, molecular mechanisms require further elucidation.

Pathology of Ground Squirrels in a Research Colony.

This paper presents a retrospective review of the postmortem findings in a colony of wild-caught ground squirrels used in medical research. The species included in this study were Richardson's ground squirrel Urocitellus richardsonii, Columbian ground squirrel Urocitellus columbianus and golden-mantled ground squirrel Callospermophilus lateralis. The pathologic findings in 160 ground squirrels from this colony demonstrated a wide variety of conditions, with chronic nephritis and hepatic adenomas being the most frequent overall. All animals with gross lesions of chronic interstitial nephritis had both glomerular and tubulointerstitial disease upon microscopic examination. As the first review of pathology in a research colony of ground squirrels. this study provides data for use in comparative studies about rodent diseases and important information for those who maintain such animals for research.

Novel Long-Acting GLP-2 Analogue, FE 203799 (Apraglutide), Enhances Adaptation and Linear Intestinal Growth in a Neonatal Piglet Model of Short Bowel Syndrome with Total Resection of the Ileum.

BACKGROUND: Glucagon-like peptide-2 (GLP-2) is an intestinotrophic factor released from L-cells in the ileum, a segment commonly resected or atretic in neonatal short bowel syndrome (SBS). In piglets, ileal resection decreases intestinal adaptation and endogenous GLP-2 production, whereas exogenous replacement promotes adaptation. In this study, we determined the effect of a novel long-acting GLP-2 analogue, FE 203799 (FE; apraglutide), upon intestinal growth, adaptation, and function in neonatal SBS piglets without ileum. METHODS: Neonatal piglets were randomized to saline (n = 10) vs FE treatment (n = 8). All piglets underwent 75% intestinal resection with jejunocolic anastomosis and were pair-fed parenteral and enteral nutrition. Saline and FE (5 mg/kg) treatments were administered subcutaneously on days 0 and 4. On day 6, 24-hour fecal samples were collected for subsequent nutrient analysis. On day 7, small-intestinal length and weight were measured and tissue collected for analyses. RESULTS: On day 7, saline and FE-treated piglets were healthy and gained equivalent weight (P = 0.12). Compared with saline piglets, FE-treated piglets had lower fecal fat (P = 0.043) and energy (P = 0.043) losses and exhibited intestinal lengthening (P = 0.001), greater small-intestinal weight (P = 0.004), longer villus height (P = 0.027), and greater crypt depth (P = 0.054). CONCLUSIONS: The subcutaneous GLP-2 analogue, FE, enhanced intestinal adaptation in a neonatal model of SBS without ileum. The observed intestinal lengthening with FE treatment was unique compared with our prior experience with native GLP-2 in this same model and has important clinical implications for treating neonatal SBS. At this developmental stage, growth in the intestine, if augmented, could accelerate weaning from parenteral nutrition.

Surgical Anatomy Does Not Affect the Progression of Intestinal Failure-Associated Liver Disease in Neonatal Piglets.

BACKGROUND: Intestinal failure-associated liver disease (IFALD) causes significant morbidity in neonates with short bowel syndrome (SBS) dependent on parenteral nutrition (PN). Resected ileum, with loss of the ileocecal valve (ICV), is the most common anatomy in SBS, yet its impact on IFALD has not been adequately studied. METHODS: Neonatal piglets were randomized to 75% intestinal resection with jejunocolic anastomosis (JC, n = 12), 75% resection with jejunoileal anastomosis and intact ICV (JI, n = 13), PN-fed sham (sham, n = 14), or sow-fed control (SF, n = 8). Surgical and sham piglets received 100% PN for 14 days before bile flow was measured and blood chemistry, liver pathology, jejunal permeability, and bacterial translocation were assessed. RESULTS: Bile flow was lower for PN-fed compared with SF (P = .002) but not different between the PN-fed groups. Total bilirubin (P = .03) and liver pathology (P < .001) were greater in PN-fed than SF groups but not different between PN-fed groups. Serum bile acids were increased in sham (P = .01) but not different between SBS groups. PN-fed piglets with sepsis had lower bile flow (P = .001) and increased bilirubin (P = .04). Neither jejunal permeability nor bacterial translocation were different between JC, JI, or sham groups. CONCLUSION: Contrary to our hypothesis, the remnant anatomy does not appear to worsen the progression of IFALD. However, the role of sepsis in IFALD should be further explored, in addition to other mechanisms, including PN factors, host immune responses, and intestinal bacterial dysbiosis.

The associated contributions of p53 and the DNA mismatch repair protein Msh6 to spontaneous tumorigenesis.

DNA mismatch repair (MMR) is a highly conserved system that repairs DNA adducts acquired during replication, as well as some forms of exogenous/endogenous DNA damage. Additionally, MMR proteins bind to DNA adducts that are not removed by MMR and influence damage-response mechanisms other than repair. Hereditary non-polyposis colorectal cancer, as well as mouse models for MMR deficiency, illustrate that MMR proteins are required for maintenance of genetic stability and tumor suppression. In both humans and mice, the phenotype associated with Msh6-associated tumorigenesis is distinct from that of Msh2. In this study, we hypothesized that Msh6-/-;p53+/- mice would display earlier tumor onset than their Msh6-/- or p53+/- counterparts, indicating that concomitant loss of these two tumor suppressors contributes to tumorigenesis via mechanisms that are only partially interrelated. We generated a Msh6-/-;p53+/- mouse model which succumbed to malignant disease at an accelerated rate and with a tumor spectrum distinct from both Msh6-/- and p53+/- models. Alteration of tumor phenotype in the Msh6-/-;p53+/- mice included a marked increase in microsatellite instability that was associated with loss of heterozygosity of the remaining p53 allele. Also, genetic instability was inversely correlated with survival. This manuscript marks the first in vivo investigation into the association between Msh6 and p53, and their combined role in the suppression of spontaneous tumorigenesis, cell survival and genomic stability. Our results support the hypothesis that p53 and Msh6 are functionally interrelated and that, with concomitant mutation, these tumor suppressors act together to accelerate tumorigenesis.

A lack of DNA mismatch repair on an athymic murine background predisposes to hematologic malignancy.

Inheritance of a germline mutation in one of the DNA mismatch repair genes predisposes human individuals to hereditary nonpolyposis colorectal cancer, characterized by development of tumors predominantly in the colon, endometrium, and gastrointestinal tract. Mice heterozygous for a mismatch repair-null mutation generally do not have an increased risk of neoplasia. However, mice constitutively lacking mismatch repair are prone to tumor development from an early age, particularly thymic lymphomas. Mismatch repair-deficient mice crossed to Apc(+/-) mice develop an increased spontaneous intestinal tumor incidence, demonstrating that the tumor spectrum can be genetically influenced. Here, we bred Msh2- and Msh6-deficient mice to athymic nude mice, hypothesizing that a broader tumor spectrum may be observed if mice are able to survive longer without succumbing to thymic lymphomas. However, Msh2(-/-);Foxn1(nu/nu) and Msh6(-/-);Foxn1(nu/nu) mice developed primarily early-onset lymphoblastic lymphomas. Using B-cell-specific markers, we found these tumors to be predominately B-cell in origin. The development of hematologic malignancy in the mouse, even in the absence of a thymus, parallels the development of B- and T-cell lymphoma and leukemia in the few rare mismatch repair-null human patients that have been identified. The persistent development of hematologic malignancy both in the mouse and in human patients deficient in mismatch repair leads us to implicate mismatch repair as an important repair mechanism in normal B- and T-cell development. Thus, mismatch repair-deficient mice may prove to be a good model to study human hematologic malignancy.

Differential Effects on Intestinal Adaptation Following Exogenous Glucagon-Like Peptide 2 Therapy With and Without Enteral Nutrition in Neonatal Short Bowel Syndrome [Formula: see text].

BACKGROUND: We aim to study the efficacy of exogenously administered glucagon-like peptide 2 (GLP-2) on intestinal adaptation in 2 preclinical models of neonatal short bowel syndrome (SBS) according to remnant intestinal anatomy, with and without ileum. Furthermore, we aim to determine if this adaptive effect was potentiated with enteral nutrition (EN). METHODS: Neonatal piglets were block-randomized to 75% mid-intestinal (JI group, retains ileum) or distal-intestinal (JC group, has no ileum) resection or no resection (sham control) and GLP-2 treatment (11 nmol/kg/d) or saline control for 7 days. Piglets received nutrition support, either 100% parenteral nutrition (PN; 0% EN, n = 32 in total) or 80% PN + 40% EN (n = 28 in total). Adaptation was assessed by morphological and histological changes, as well as RT quantitative polymerase chain reaction of nutrient transporters and tight junctional proteins and fat absorption. Data are analyzed by 3-way analysis of variance (ANOVA) and 2-way ANOVA per EN level. RESULTS: GLP-2 treatment lengthened villi, deepened crypts, and improved intestinal weight in the remnant intestine of JC piglets. EN was a more potent adaptive stimulus for JI piglets. Small intestinal lengthening occurred only in the JI group, when given EN. There was no difference in total fat absorption and messenger RNA expression of nutrient transporters and tight junctional proteins. CONCLUSIONS: GLP-2 administration augmented structural adaptation in JC piglets with distal intestinal resection. Given JI anatomy, further stimulation by GLP-2 treatment over innate adaptation and stimulation by EN was modest and restricted to ileum. The differential effect of GLP-2 in neonatal SBS, depending on remnant anatomy, has important implications for clinical translation and planning of clinical trials.

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.