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Limited work has focused on fibroblast growth factor-19 (FGF19) secretion and function in the perinatal period. FGF19 is a potent growth factor that coordinates development of the brain, eye, inner ear, and skeletal system in the embryo, but after birth, FGF19 transitions to be an endocrine regulator of the classic pathway of hepatic bile acid synthesis. FGF19 has emerged as a mediator of metabolism and bile acid synthesis in aged animals and adults in the context of liver disease and metabolic dysfunction. FGF19 has also been shown to have systemic insulin-sensitizing and skeletal muscle hypertrophic effects when induced or supplemented at supraphysiological levels in adult rodent models. These effects could be beneficial to improve growth and nutritional outcomes in preterm infants, which are metabolically resistant to the anabolic effects of enteral nutrition. Existing clinical data on FGF19 secretion and function in the perinatal period in term and preterm infants has been equivocal. Studies in pigs show that FGF19 expression and secretion are upregulated with gestational age and point to molecular and endocrine factors that may be involved. Work focused on FGF19 in pediatric diseases suggests that augmentation of FGF19 secretion by activation of gut FXR signaling is associated with benefits in diseases such as short bowel syndrome, parenteral nutrition-associated liver disease, and biliary atresia. Future work should focus on characterization of FGF19 secretion and the mechanism underpinning the transition of FGF19 function as an embryological growth factor to metabolic and bile acid regulator. [ABSTRACT FROM AUTHOR]

Extensive bowel resection can lead to short bowel syndrome and intestinal failure. Resection-induced dysbiosis may be related to the specific anatomic site of resection and influences the disease progression. Although patients with end-jejunostomy are at high risk for intestinal failure, preservation of the ileocecal valve and colon counteracts this risk. The present study investigated the role of the cecum in maintaining microbial homeostasis after different types of small bowel resection. Male C57BL6/J mice were anesthetized by intraperitoneal injection of ketamine-xylazine and received extended ileocecal resection (extended ICR), limited ileocecal resection (limited ICR), or mid-small bowel resection (SBR). Stool samples were collected before surgery and between postoperative days 2-7, for 16S rRNA gene sequencing. Only extended ICR, but neither limited ICR nor SBR, induced intestinal insufficiency. α-Diversity was reduced in both ICR variants but not after SBR. All resections resulted in an increase in Proteobacteria. Pathobionts, such as Clostridia, Shigella, and Enterococcus, increased after SBR while Muribaculaceae, Lactobacillus, and Lachnospiraceae decreased. Limited ICR resulted in an increase of members of the Clostridium sensu stricto group, Terrisporobacter and Enterococcus and a decrease of Muribaculaceae. The increase of Enterococcus was even more pronounced after extended ICR while Muribaculaceae and Akkermansia were dramatically reduced. Both ICR variants caused a decrease in steroid biosynthesis and glycosaminoglycan degradation-associated pathways, suggesting altered bile acid transformation and mucus utilization. [ABSTRACT FROM AUTHOR]

Intestinal failure-associated liver disease is a major morbidity associated with short bowel syndrome. We sought to determine if the obesity-resistant mouse strain (129S1/SvImJ) conferred protection from liver injury after small bowel resection (SBR). Using a parenteral nutrition-independent model of resection-associated liver injury, C57BL/6J and 129S1/SvImJ mice underwent a 50% proximal SBR or sham operation. At postoperative week 10, hepatic steatosis, fibrosis, and cholestasis were assessed. Hepatic and systemic inflammatory pathways were evaluated using oxidative markers and abundance of tissue macrophages. Potential mechanisms of endotoxin resistance were also explored. Serum lipid levels were elevated in all mouse lines. Hepatic triglyceride levels were no different between mouse strains, but there was an increased accumulation of free fatty acids in the C57BL/6J mice. Histological and serum markers of hepatic fibrosis, steatosis, and cholestasis were significantly elevated in resected C57BL/6J SBR mice as well as oxidative stress markers and macrophage recruitment in both the liver and visceral white fat in C57BL/6J mice compared with sham controls and the 129S1/SvImJ mouse line. Serum endotoxin levels were significantly elevated in C57BL/6J mice with significant elevation of hepatic TLR4 and reduction in PPARα expression levels. Despite high levels of serum lipids, 129S1/SvImJ mice did not develop liver inflammation, fibrosis, or cholestasis after SBR, unlike C57BL/6J mice. These data suggest that the accumulation of hepatic free fatty acids as well as increased endotoxin-driven inflammatory pathways through PPARα and TLR4 contribute to the liver injury seen in C57BL/6J mice with short bowel syndrome. NEW & NOTEWORTHY Unlike C57BL/6 mice, the 129S1/SvImJ strain is resistant to liver inflammation and injury after small bowel resection. These disparate outcomes are likely due to the accumulation of hepatic free fatty acids as well as increased endotoxin-driven inflammatory pathways through PPARα and TLR4 in C57BL/6 mice with short bowel syndrome. [ABSTRACT FROM AUTHOR]

This study provides novel insight into the mechanisms of intestinal dysmotility following massive small bowel resection. We show that 2 wk after bowel resection in rats, impaired intestinal motility was associated with loss of interstitial cells of Cajal (ICC; downregulation of transmembrane member 16A (TMEM16A) and c-kit expression) as well as with decreased vimentin, desmin, and ghrelin levels. Impaired intestinal motility led to a decrease in final body weight, suggesting less effective nutrient absorption. The purpose of this study was to evaluate the mechanisms of intestinal motility in a rat model of short bowel syndrome (SBS). Rats were divided into three groups: Sham rats underwent bowel transection; SBS-NSI rats underwent a 75% bowel resection and presented with normal intestinal size (NSI) at euthanasia and hypermotility patterns; SBS-DYS showed dysmotile (DYS) enlarged intestine and inhibited motility patterns. Animals were euthanized after 2 wk. Illumina's digital gene expression (DGE) analysis was used to determine the intestinal motility-related gene expression profiling in mucosal samples. Intestinal motility-related and ICC genes and protein expression in intestinal muscle layer were determined using real-time PCR, Western blotting, and immunohistochemistry. Gastrointestinal tract motility was studied by microcomputer tomography. From 10 Ca2+ signaling pathway-related genes, six genes in jejunum and seven genes in ileum were downregulated in SBS vs. Sham animals. Downregulation of TMEM16A mRNA and protein was confirmed by real-time PCR. Rapid intestinal transit time in SBS-NSI rats correlated with a mild decrease in TMEM16A, c-kit, and vimentin mRNA and protein expression (vs/. Sham animals). SBS-DYS rats demonstrated enlarged intestinal loops and delayed small intestinal emptying (on imaging studies) that were correlated with marked downregulation in TMEM16A, c-kit, vimentin, and ghrelin mRNA and protein levels compared with the other two groups. In conclusion, 2 wk following massive bowel resection in rats, impaired intestinal motility was associated with decreased vimentin and ghrelin gene and protein levels as well as loss of ICC (c-kit and TMEM16A). NEW & NOTEWORTHY This study provides novel insight into the mechanisms of intestinal dysmotility following massive small bowel resection. We show that 2 weeks after bowel resection in rats, impaired intestinal motility was associated with loss of interstitial cells of Cajal (downregulation of TMEM 16A, and c-kit expression) as well as with decreased vimentin, desmin, and ghrelin levels. Impaired intestinal motility led to decrease in final body weight, suggesting less effective nutrient absorption. [ABSTRACT FROM AUTHOR]

Short bowel syndrome (SBS) is associated with changes in the intestinal microbiome and marked local and systemic inflammation. There is also a late complication of SBS, intestinal failure associated liver disease (IFALD) in which hepatic steatosis progresses to cirrhosis. Most patients with SBS arrive at massive intestinal resection after a contaminating intraabdominal catastrophe and have a history of exposure to broad-spectrum antibiotics. We therefore investigated whether the administration of broad-spectrum antibiotics in conjunction with SBS in zebrafish (ZF) would replicate these systemic effects observed in humans to identify potentially druggable targets to aid in the management of SBS and resulting IFALD. In zebrafish with SBS, broad-spectrum antibiotics altered the microbiome, decreased inflammation, and reduced the development of hepatic steatosis. After two weeks of broad-spectrum antibiotics, these fish exhibited decreased alpha diversity, with less variation in microbial community composition between SBS and sham fish. Additionally, administration of broad-spectrum antibiotics was associated with decreased expression of intestinal toll-like receptor 4 (tlr4), increased expression of the intestinal gene encoding the Farnesoid X receptor (fxr), decreased expression of downstream hepatic cyp7a1, and decreased development of hepatic steatosis. SBS in zebrafish reproducibly results in increased epithelial surface area as occurs in human patients who demonstrate intestinal adaptation, but antibiotic administration in zebrafish with SBS reduced these gains with increased cell death in the intervillus pocket that contains stem/progenitor cells. These alternate states in SBS zebrafish might direct the development of future human therapies. NEW & NOTEWORTHY In a zebrafish model that replicates a common clinical scenario, systemic effects of the administration of broad-spectrum antibiotics in a zebrafish model of SBS identified two alternate states that led to the establishment of fat accumulation in the liver or its absence. Broad-spectrum antibiotics given to zebrafish with SBS over 2 wk altered the intestinal microbiome, decreased intestinal and hepatic inflammation, and decreased hepatic steatosis. [ABSTRACT FROM AUTHOR]

Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) gene mutations are a risk factor for Crohn's disease and also associated with worse outcome in short bowel syndrome (SBS) patients independent of the underlying disease. The aim of this study was to analyze the effect of Nod2 deficiency on barrier function and stool microbiome after extensive ileocecal resection in mice. Male C57BL6/J wild-type (WT) and Nod2-knockout (KO) mice underwent 40% ileocecal resection. Sham control mice received simple transection of the ileum. Clinical outcome was monitored daily. Barrier function was measured with Ussing chambers using FITC-4-kDa-Dextran flux, transmucosal electrical resistance, and dilution potentials. Immunofluorescence of claudin-2 was studied. Composition of the stool microbiome was assessed by 16S rRNA gene sequencing. Resected Nod2-KO mice had impaired clinical outcome compared with resected WT mice. This was accompanied by increased stool water contents and increased plasma aldosterone. Histomorphological adaptation was independent of Nod2. Barrier function studies revealed impaired sodium to chloride permeability and altered claudin-2 localization in the absence of Nod2. Resection induced decreases of bacterial diversity and a shift of bacteriodetes-to-firmicutes ratios. Ileum and cecum resection-induced increase in proteobacteria was absent in Nod2-deficient mice. Verrucomicrobia were temporarily increased in Nod2-KO mice. Nod2 deficiency functionally impairs adaptation to short bowel syndrome via a lesser increase of epithelial sodium pore permeability, altered epithelial barrier function, and the microbiome. NEW & NOTEWORTHYNOD2 gene mutations are associated with the development of severe short bowel syndrome and intestinal failure. The influence of Nod2 mutations on intestinal adaptation in experimental short bowel syndrome has not been studied yet. Here, we provide data that Nod2 deficiency worsens clinical outcome and functional adaptation under SBS conditions in mice, indicating that NOD2 is required for successful adaptation after ileocecal resection. [ABSTRACT FROM AUTHOR]

Mortality associated with liver disease has been observed in patients with short bowel syndrome (SBS); however, its mechanism remains unclear, but bile acid (BA) dysmetabolism has been proposed as a possible cause. The farnesoid X receptor (FXR) is the key regulator of BA synthesis. Here, we showed that, in a rat model of short bowel resection associated with liver disease (SBR-ALD), the BA composition of hepatic tissues reflected a larger proportion of primary and secondary unconjugated BAs, whereas that of the colon contents and serum showed an increased ratio of secondary unconjugated BAs. Both hepatic and intestinal regulation of BA synthesis was characterized by a blunted hepatic FXR activation response. The mRNA expression levels of cholesterol 7a-hydroxylase (CYP7A1), sterol 12a-hydroxylase (CYP8B1), and sterol 27 hydroxylase (CYP27A1), the key enzymes in BA synthesis, were upregulated. After intervention with the FXR agonist GW4064, both the liver histology and serum transaminase activity were improved, which demonstrated the attenuation of SBR-ALD. The BA compositions of hepatic tissue, the colon contents, and serum recovered and were closer to those of the sham group. The expression levels of hepatic FXR increased, and its target genes were activated. Consistent with this, the expression levels of CYP7A1, CYP8B1, and CYP27A1 were downregulated. Ileum tissue FXR and its target genes were slightly elevated. This study showed that the FXR agonist GW4064 could correct BA dysmetabolism to alleviate hepatotoxicity in SBR animals. GW4064 intervention resulted in a decrease in fecal bile excretion and elevated plasma/hepatic conjugated BA levels. GW4064 increased the reabsorption of conjugated BAs by inducing apical sodium-dependent bile salt transporter expression in the ileum. Concomitantly, FXR activation in the presence of GW4064 decreased BA production by repressing the expression of key synthetases, including CYP7A1, CYP8B1, and CYP27A1. These findings provide a clinical research direction for the prevention of liver disease in patients with SBS. [ABSTRACT FROM AUTHOR]

Intestinal adaptation (IA) is a critical response to increase epithelial surface area after intestinal loss. Short bowel syndrome (SBS) may follow massive intestinal resection in human patients, particularly without adequate IA. We previously validated a model in zebrafish (ZF) that recapitulates key SBS pathophysiological features. Previous RNA sequencing in this model identified upregulation of genes in the Wnt and Hippo pathways. We therefore sought to identify the timeline of increasing cell proliferation and considered the signaling that might underpin the epithelial remodeling of IA in SBS. SBS was created in a ZF model as previously reported and compared with sham fish with and without exposure to monensin, an ionophore known to inhibit canonical Wnt signaling. Rescue of the monensin effects was attempted with a glycogen synthase kinase 3 inhibitor that activates wnt signaling, CHIR-99021. A timeline was constructed to identify peak cellular proliferation, and the Wnt and Hippo pathways were evaluated. Peak stem cell proliferation and morphological changes of adaptation were identified at 7 days. Wnt inhibition diminished IA at 2 wk and resulted in activation of genes of the Wnt/β-catenin and Yes-associated protein (YAP)/Hippo pathway. Increased cytoplasmic YAP was observed in monensin-treated SBS fish. Genes of the WASP-interacting protein (WIP) pathway were elevated during Wnt blockade. In conclusion, cellular proliferation and morphological changes accompany SBS even in attempted Wnt blockade. Wnt/β-catenin, YAP/Hippo pathway, and WIP pathway genes increase during early Wnt blockade. Further understanding of the effects of Wnt and YAP pathway signaling in proliferating stem cells might enrich our knowledge of targets to assist IA. [ABSTRACT FROM AUTHOR]

Enteroendocrine L cells and glucagon-like peptide 2 (GLP-2) secretion are activated in the intestinal adaptation process following bowel resection in patients with short bowel syndrome. We hypothesized that enteral activation of Takeda G protein-coupled receptor 5 (TGR5), expressed in enteroendocrine L cells, could augment endogenous GLP-2 secretion and the intestinal adaptation response. Our aim was to assess the efficacy of different TGR5 agonists to stimulate GLP-2 secretion and intestinal adaptation in a piglet short-bowel model. In study 1, parenterally fed neonatal pigs (n = 6/group) were gavaged with vehicle, olive extract (OE; 10 or 50 mg/kg), or ursolic acid (UA; 10 mg/kg), and plasma GLP-2 was measured for 6 h. In study 2, neonatal pigs (n = 6-8/group) were subjected to transection or 80% mid-small intestine resection and, after 2 days, assigned to treatments for 10 days as follows: 1) transection + vehicle (sham), 2) resection + vehicle (SBS), 3) resection + 30 mg UA (SBS + UA), and 4) resection + 180 mg/kg OE (SBS + OE). We measured plasma GLP-2, intestinal histology, cell proliferation, and gene expression, as well as whole body citrulline-arginine kinetics and bile acid profiles. In study 1, GLP-2 secretion was increased by UA and tended to be increased by OE. In study 2, SBS alone, but not additional treatment with either TGR5 agonist, resulted in increased mucosal thickness and crypt cell proliferation in remnant jejunum and ileum sections. SBS increased biliary and ileal concentration of bile acids and expression of inflammatory and farnesoid X receptor target genes, but these measures were suppressed by UA treatment. In conclusion, UA is an effective oral GLP-2 secretagogue in parenterally fed pigs but is not capable of augmenting GLP-2 secretion or the intestinal adaptation response after massive small bowel resection. NEW & NOTEWORTHY Therapeutic activation of endogenous glucagon-like peptide 2 (GLP-2) secretion is a promising strategy to improve intestinal adaptation in patients with short bowel syndrome. This study in neonatal pigs showed that oral supplementation with a selective Takeda G protein-coupled receptor 5 (TGR5) agonist is an effective approach to increase GLP-2 secretion. The results warrant further study to establish a more potent oral TGR5 agonist that can effectively improve intestinal adaptation in pediatric patients with SBS. [ABSTRACT FROM AUTHOR]

Notch signaling is thought to act to drive cell versification in the lining of the small intestine. The purpose of the present study was to evaluate the role of the Notch signaling pathway in stem cell differentiation in the late stages of intestinal adaptation after massive small bowel resection in a rat. Male Sprague- Dawley rats were randomly assigned to one of two experimental groups of eight rats each: Sham rats underwent bowel transection and reanastomosis, while SBS rats underwent 75% small bowel resection. Rats were euthanized on day 14. Illumina's Digital Gene Expression (DGE) analysis was used to determine Notch signaling gene expression profiling. Notch-related gene and protein expression was determined using real-time PCR, Western blot analysis, and immunohistochemistry. From seven investigated Notch-related (by DGE analysis) genes, six genes were upregulated in SBS vs. control animals with a relative change in gene expression level of 20% or more. A significant upregulation of Notch signaling-related genes in resected animals was accompanied by a significant increase in Notch-1 protein levels (Western blot analysis) and a significant increase in the number of Notch1 and Hes1 (target gene)-positive cells (immunohistochemistry) compared with sham animals. Evaluation of cell differentiation has shown a strong increase in total number of absorptive cells (unchanged secretory cells) compared with control rats. In conclusion, 2 wk after bowel resection in rats, stimulated Notch signaling directs the crypt cell population toward absorptive progenitors. [ABSTRACT FROM AUTHOR]

Intestinal resection resulting in short bowel syndrome (SBS) carries a heavy burden of long-term morbidity, mortality, and cost of care, which can be attenuated with strategies that improve intestinal adaptation. SBS infants fed human milk, compared with formula, have more rapid intestinal adaptation. We tested the hypothesis that the major noncaloric human milk oligosaccharide 2'-fucosyllactose (2'-FL) contributes to the adaptive response after intestinal resection. Using a previously described murine model of intestinal adaptation, we demonstrated increased weight gain from 21 to 56 days (P < 0.001) and crypt depth at 56 days (P < 0.0095) with 2'-FL supplementation after ileocecal resection. Furthermore, 2'-FL increased small bowel luminal content microbial alpha diversity following resection (P < 0.005) and stimulated a bloom in organisms of the genus Parabacteroides (log2-fold = 4.1, P = 0.035). Finally, transcriptional analysis of the intestine revealed enriched ontologies and pathways related to antimicrobial peptides, metabolism, and energy processing. We conclude that 2'-FL supplementation following ileocecal resection increases weight gain, energy availability through microbial community modulation, and histological changes consistent with improved adaptation. [ABSTRACT FROM AUTHOR]

Loss of significant intestinal length from congenital anomaly or disease may lead to short bowel syndrome (SBS); intestinal failure may be partially offset by a gain in epithelial surface area, termed adaptation. Current in vivo models of SBS are costly and technically challenging. Operative times and survival rates have slowed extension to transgenic models. We created a new reproducible in vivo model of SBS in zebrafish, a tractable vertebrate model, to facilitate investigation of the mechanisms of intestinal adaptation. Proximal intestinal diversion at segment 1 (S1, equivalent to jejunum) was performed in adult male zebrafish. SBS fish emptied distal intestinal contents via stoma as in the human disease. After 2 wk, S1 was dilated compared with controls and villus ridges had increased complexity, contributing to greater villus epithelial perimeter. The number of intervillus pockets, the intestinal stem cell zone of the zebrafish increased and contained a higher number of bromodeoxyuridine (BrdU)-labeled cells after 2 wk of SBS. Egf receptor and a subset of its ligands, also drivers of adaptation, were upregulated in SBS fish. Igf has been reported as a driver of intestinal adaptation in other animal models, and SBS fish exposed to a pharmacological inhibitor of the Igf receptor failed to demonstrate signs of intestinal adaptation, such as increased inner epithelial perimeter and BrdU incorporation. We describe a technically feasible model of human SBS in the zebrafish, a faster and less expensive tool to investigate intestinal stem cell plasticity as well as the mechanisms that drive intestinal adaptation. [ABSTRACT FROM AUTHOR]

Short bowel syndrome (SBS) is a devastating condition in which insufficient small intestinal surface area results in malnutrition and dependence on intravenous parenteral nutrition. There is an increasing incidence of SBS, particularly in premature babies and newborns with congenital intestinal anomalies. Tissue-engineered small intestine (TESI) offers a therapeutic alternative to the current standard treatment, intestinal transplantation, and has the potential to solve its biggest challenges, namely donor shortage and life-long immunosuppression. We have previously demonstrated that TESI can be generated from mouse and human small intestine and histologically replicates key components of native intestine. We hypothesized that TESI also recapitulates native small intestine function. Organoid units were generated from mouse or human donor intestine and implanted into genetically identical or immunodeficient host mice. After 4 wk, TESI was harvested and either fixed and paraffin embedded or immediately subjected to assays to illustrate function. We demonstrated that both mouse and human tissue-engineered small intestine grew into an appropriately polarized sphere of intact epithelium facing a lumen, contiguous with supporting mesenchyme, muscle, and stem/progenitor cells. The epithelium demonstrated major ultrastructural components, including tight junctions and microvilli, transporters, and functional brush-border and digestive enzymes. This study demonstrates that tissue-engineered small intestine possesses a well-differentiated epithelium with intact ion transporters/channels, functional brush-border enzymes, and similar ultrastructural components to native tissue, including progenitor cells, whether derived from mouse or human cells. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Effective therapies are limited for patients with parenteral nutritiondependent short bowel syndrome. We previously showed that intestinal expression of the transcriptional coregulator tetradecanoyl phorbol acetate-induced sequence 7 (tis7) is markedly increased during the adaptive response following massive small bowel resection and tis7 plays a role in normal gut lipid metabolism. Here, we further explore the functional implications of tis7 deletion in intestinal lipid metabolism and the adaptive response following small bowel resection. Intestinal tis7 transgenic (tis7tg), tis7-/-, and wild-type (WT) littermates were subjected to 50% small bowel resection. Mice were fed a control or a high-saturated-fat (42% energy) diet for 21 days. Survival, body weight recovery, lipid absorption, mucosal lipid analysis, and the morphometric adaptive response were analyzed. Quantitative real-time PCR was performed to identify tis7 downstream gene targets. Postresection survival was markedly reduced in high-fat, but not control, diet-fed tis7-/- mice. Decreased survival was associated with anastomotic inflammation and intestinal obstruction postresection. High-fat, but not control, diet-fed tis7-/- mice had increased intestinal IL-6 expression. Intestinal lipid trafficking was altered in tis7-/- compared with WT mice postresection. In contrast, high-fat diet-fed tis7tg mice had improved survival postresection compared with WT littermates. High-fat diet feeding in the setting of tis7 deletion resulted in postresection anastomotic inflammation and small bowel obstruction. Tolerance of a calorie-rich, high-fat diet postresection may require tis7 and its target genes. The presence of luminal fat in the setting of tis7 deletion promotes an intestinal inflammatory response postresection. [ABSTRACT FROM AUTHOR]

Glucagonlike peptide-2 (GLP-2) has been shown to be effective in patients with short bowel syndrome (SBS), but it is rapidly inactivated by dipeptidyl peptidase IV (DPP4). We used an orally active DPP4 inhibitor (DPP4-I), MK-0626, to determine the efficacy of this approach to promote adaptation after SBS, determined optimal dosing, and identified further functional actions in a mouse model of SBS. Ten-weekold mice underwent a 50% proximal small bowel resection. Dose optimization was determined over a 3-day post-small bowel resection period. The established optimal dose was given for 7, 30, and 90 days and for 7 days followed by a 23-day washout period. Adaptive response was assessed by morphology, intestinal epithelial cell (IEC) proliferation (proliferating cell nuclear antigen), epithelial barrier function (transepithelial resistance), RT-PCR for intestinal transport proteins and GLP-2 receptor, IGF type 1 receptor, and GLP-2 plasma levels. Glucose-stimulated sodium transport was assessed for intestinal absorptive function. Seven days of DPP4-I treatment facilitated an increase in GLP-2 receptor levels, intestinal growth, and IEC proliferation. Treatment led to differential effects over time, with greater absorptive function at early time points and enhanced proliferation at later time points. Interestingly, adaptation continued in the group treated for 7 days followed by a 23-day washout. DPP4-I enhanced IEC proliferative action up to 90 days postresection, but this action seemed to peak by 30 days, as did GLP-2 plasma levels. Thus DPP4-I treatment may prove to be a viable option for accelerating intestinal adaptation with SBS. [ABSTRACT FROM AUTHOR]

Short bowel syndrome (SBS) is a frequent complication after intestinal resection in infants suffering from intestinal disease. We tested whether treatment with the intestinotrophic hormone glucagon-like peptide-2 (GLP-2) increases intestinal volume and function in the period immediately following intestinal resection in preterm pigs. Preterm pigs were fed enterally for 48 h before undergoing resection of 50% of the small intestine and establishment of a jejunostomy. Following resection, pigs were maintained on total parenteral nutrition (TPN) without (SBS, n = 8) or with GLP-2 treatment (3.5 μg/kg body wt per h, SBSGLP-2, n = 7) and compared with a group of unresected preterm pigs (control, n 5). After 5 days of TPN, all piglets were fed enterally for 24 h, and a nutrient balance study was performed. Intestinal resection was associated with markedly reduced endogenous GLP-2 levels. GLP-2 increased the relative absorption of wet weight (46 vs. 22%), energy (79 vs. 64%), and all macronutrients (all parameters P < 0.05). These findings were supported by a 200% increase in sucrase and maltase activities, a 50% increase in small intestinal epithelial volume (P < 0.05), as well as increased DNA and protein contents and increased total protein synthesis rate in SBS+GLP-2 vs. SBS pigs (+100%, P < 0.05). Following intestinal resection in preterm pigs, GLP-2 induced structural and functional adaptation, resulting in a higher relative absorption of fluid and macronutrients. GLP-2 treatment may be a promising therapy to enhance intestinal adaptation and improve digestive function in preterm infants with jejunostomy following intestinal resection. [ABSTRACT FROM AUTHOR]

Glucagon-like peptide-2 (GLP-2) is a nutrient-dependent, proglucagon- derived gut hormone that shows promise for the treatment of short bowel syndrome (SBS). Our objective was to investigate how combination GLP-2 + enteral nutrients (EN) affects intestinal adaption in a rat model that mimics severe human SBS and requires parenteral nutrition (PN). Male Sprague-Dawley rats were assigned to one of five groups and maintained with PN for 18 days: total parenteral nutrition (TPN) alone, TPN + GLP-2 (100 μg∙kg-1∙day-1), PN + EN + GLP-2(7 days), PN + EN + GLP-2(18 days), and a nonsurgical oral reference group. Animals underwent massive distal bowel resection followed by jejunocolic anastomosis and placement of jugular catheters. Starting on postoperative day 4, rats in the EN groups were allowed ad libitum access to EN. Groups provided PN + EN + GLP-2 had their rate of PN reduced by 0.25 ml/day starting on postoperative day 6. Groups provided PN + EN + GLP-2 demonstrated significantly greater body weight gain with similar energy intake and a safe 80% reduction in PN compared with TPN ± GLP-2. Groups provided PN + EN + GLP-2 for 7 or 18 days showed similar body weight gain, residual jejunal length, and digestive capacity. Groups provided PN + EN + GLP-2 showed increased jejunal GLP-2 receptor (GLP-2R), insulin-like growth factor-I (IGF-I), and IGF-binding protein-5 (IGFBP-5) expression. Treatment with TPN + GLP-2 demonstrated increased jejunal expression of epidermal growth factor. Cessation of GLP-2 after 7 days with continued EN sustained the majority of intestinal adaption and significantly increased expression of colonic proglucagon compared with PN + EN + GLP-2 for 18 days, and increased plasma GLP-2 concentrations compared with TPN alone. In summary, EN potentiate the intestinotrophic actions of GLP-2 by improving body weight gain allowing for a safe 80% reduction in PN with increased jejunal expression of GLP-2R, IGF-I, and IGFBP-5 following distal bowel resection in the rat. [ABSTRACT FROM AUTHOR]

Numerous cytokines have been shown to affect epithelial cell differentiation and proliferation through epithelial-mesenchymal interaction. Growing evidence suggests that platelet-derived growth factor (PDGF) signaling is an important mediator of these interactions. The purpose of this study was to evaluate the effect of PDGF-α on enterocyte turnover in a rat model of short bowel syndrome (SBS). Male rats were divided into four groups: Sham rats underwent bowel transection, Sham-PDGF-α rats underwent bowel transection and were treated with PDGF-α, SBS rats underwent a 75% bowel resection, and SBS-PDGF-α rats underwent bowel resection and were treated with PDGF-α. Parameters of intestinal adaptation, enterocyte proliferation and apoptosis were determined at euthanasia. Illumina's Digital Gene Expression analysis was used to determine PDGF-related gene expression profiling. PDGF-α and PDGF-α receptor (PDGFR-α) expression was determined by real-time PCR. Western blotting was used to determine p-ERK, Akt1/2/3, bax, and bcl-2 protein levels. SBS rats demonstrated a significant increase in PDGF-α and PDGFR-α expression in jejunum and ileum compared with sham animals. SBS-PDGF-α rats demonstrated a significant increase in bowel and mucosal weight, villus height, and crypt depth in jejunum and ileum compared with SBS animals. PDGF-α receptor expression in crypts increased in SBS rats (vs. sham) and was accompanied by an increased cell proliferation following PDGF-α administration. A significant decrease in cell apoptosis in this group was correlated with lower bax protein levels. In conclusion, in a rat model of SBS, PDGF-α stimulates enterocyte turnover, which is correlated with upregulated PDGF-α receptor expression in the remaining small intestine. [ABSTRACT FROM AUTHOR]

Intestinal adaptation is an important compensatory response to massive small bowel resection (SBR) and occurs because of a proliferative stimulus to crypt enterocytes by poorly understood mechanisms. Recent studies suggest the enteric nervous system (ENS) influences enterocyte proliferation. We, therefore, sought to determine whether ENS dysfunction alters resection-induced adaptation responses. Ret+/- mice with abnormal ENS function and wild-type (WT) littermates underwent sham surgery or 50% SBR. After 7 days, ileal morphology, enterocyte proliferation, apoptosis, and selected signaling proteins were characterized. Crypt depth and villus height were equivalent at baseline in WT and Ret+/- mice. In contrast after SBR, Ret+/- mice had longer villi (Ret+/- 426.7 μ± 46.0 m vs. WT 306.5 ± 7.7 μm, P < 0.001) and deeper crypts (Ret+/- 119 ± 3.4 μm vs. WT 82.4 ± 3.1 μm, P < 0.001) than WT. Crypt enterocyte proliferation was higher in Ret+/- (48.8 ± 1.3%) than WT (39.9 ± 2.1%; P < 0.001) after resection, but apoptosis rates were similar. Remnant bowel of Ret+/- mice also had higher levels of glucagon-like peptide 2 (6.2-fold, P < 0.005) and amphiregulin (4.6-fold, P < 0.001) mRNA after SBR, but serum glucagon- like peptide 2 protein levels were equal in WT and Ret+/- mice, and there was no evidence of increased c-Fos nuclear localization in submucosal neurons. Western blot confirmed higher crypt epidermal growth factor receptor (EGFR) protein levels (1.44-fold; P < 0.001) and more phosphorylated EGFR (2-fold; P < 0.003) in Ret+/- than WT mice after SBR. These data suggest that Ret heterozygosity enhances intestinal adaptation after massive SBR, likely via enhanced EGFR signaling. Reducing Ret activity or altering ENS function may provide a novel strategy to enhance adaptation attenuating morbidity in patients with short bowel syndrome. [ABSTRACT FROM AUTHOR]

Increased apoptosis in crypt enterocytes is a key feature of intestinal adaptation following massive small bowel resection (SBR). Expression of the proapoptotic factor Bax has been shown to be required for resection-induced apoptosis. It has also been demonstrated that p38-α MAPK (p38) is necessary for Bax activation and apoptosis in vitro. The present studies were designed to test the hypothesis that p38 is a key regulator of Bax activation during adaptation after SBR in vivo. Enterocyte expression of p38 was deleted by tamoxifen administration to activate villin-Cre in adult mice with a floxed Mapk14 (p38-α) gene. Proximal 50% SBR or sham operations were performed on wild-type (WT) and p38 intestinal knockout (p38-IKO) mice under isoflurane anesthesia. Mice were killed 3 or 7 days after operation, and adaptation was analyzed by measuring intestinal morphology, proliferation, and apoptosis. Bax activity was quantified by immunoprecipitation, followed by Western blotting. After SBR, p38-IKO mice had deeper crypts, longer villi, and accelerated proliferation compared with WT controls. Rates of crypt apoptosis were significantly lower in p38-IKO mice, both at baseline and after SBR. Levels of activated Bax were twofold higher in WT mice after SBR relative to sham. In contrast, activated Bax levels were reduced by 67% in mice after p38 MAPK deletion. Deleted p38 expression within the intestinal epithelium leads to enhanced adaptation and reduced levels of enterocyte apoptosis after massive intestinal resection. p38-regulated Bax activation appears to be an important mechanism underlying resection-induced apoptosis. [ABSTRACT FROM AUTHOR]

Glucagon-like peptide-2 (GLP-2) is a nutrient-dependent, proglucagon-derived hormone that is a proposed treatment for human short bowel syndrome (SBS). The objective was to determine how the timing, duration, and cessation of GLP-2 administration affect intestinal adaptation and enterocyte kinetics in a rat model of human SBS that results in intestinal failure requiring total parenteral nutrition (TPN). Rats underwent 60% jejunoileai resection plus cecectomy and jugular vein cannulation and were maintained exclusively with TPN for 18 days in these treatments: TPN control (no GLP-2); sustained GLP-2 (1-18 days); early GLP-2 (1-7 days, killed at 7 or 18 days); and delayed GLP-2 (12-18 days). Body weight gain was similar across groups, and plasma bioactive GLP-2 was significantly in- creased with coinfusion of GLP-2 (100 μg.kg-1.day-1) with TPN. GLP-2-treated rats showed significant increases in duodenum and jejunum mucosal dry mass, protein, DNA, and sucrase activity compared with TPN control. The increased jejunum cellularity reflected significantly decreased apoptosis and increased crypt mitosis and crypt fission due to GLP-2. When GLP-2 infusion stopped at 7 days, these effects were reversed at 18 days. Sustained GLP-2 infusion significantly increased duodenum length and decreased 18-day mor- tality to 0% from 37.5% deaths in TPN control (P = 0.08). Colon proglucagon expression quantified by real-time RT-qPCR was increased in TPN controls and attenuated by GLP-2 infusion; jejunal expression of the GLP-2 receptor did not differ among groups. In summary, early, sustained GLP-2 infusion reduces mortality, induces crypt fission, and is required for intestinal adaptation, whereas cessation of GLP-2 reverses gains in mucosal cellularity in a rat model of intestinal failure. [ABSTRACT FROM AUTHOR]

Angiotensin converting enzyme (ACE) has been shown to be involved in regulation of apoptosis in nonintestinal tissues. This study examined the role of ACE in the modulation of intestinal adaptation utilizing ACE knockout mice (ACE-/-). A 60% small bowel resection (SBR) was used, since this model results in a significant increase in intestinal epithelial cell (EC) apoptosis as well as proliferation. Baseline villus height, crypt depth, and intestinal EC proliferation were higher, and EC apoptosis rates were lower in ACE-/- compared with ACE+/+ mice. After SBR, EC apoptosis rates remained significantly lower in ACE-/- compared with ACE+/+ mice. Furthermore, villus height and crypt depth after SBR continued to be higher in ACE-/- mice. The finding of a lower bax-to-bcl-2 protein ratio in ACE-/- mice may account for reduced EC apoptotic rates after SBR in ACE-/- compared with ACE+/+ mice. The baseline higher rate of EC proliferation in ACE-/- compared with ACE+/+ mice may be due to an increase in the expression of several EC growth factor receptors. In conclusion, ACE appears to have an important role in the modulation of intestinal EC apoptosis and proliferation and suggests that the presence of ACE in the intestinal epithelium has a critical role in guiding epithelial cell adaptive response. [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated that the proapoptotic protein Bax plays an important role in the elevated enterocyte apoptosis that occurs during the intestinal adaptation response to massive small bowel resection (SBR). Additionally, epidermal growth factor receptor (EGFR) activation prevents SBR-induced enterocyte apoptosis. The present study aims to delineate the relationship between EGFR activity and intestinal epithelial cell apoptosis. Treatment of model intestinal epithelial cells (RIEC-18) with both a selective EGFR inhibitor (ZD1839) and EGFR small interfering RNA knockdown resulted in a dramatic increase in apoptosis, accompanied by rapid phosphorylation of p38α. Concurrently, Bax underwent conformational changes consistent with activation and translocated to mitochondria. In contrast, EGF stimulation enhanced cell survival by attenuating p38α phosphorylation, Bax conformational change, mitochondrial trafficking, and apoptosis. These results demonstrate that that diminished EGFR activity initiates the intrinsic pathway of apoptosis through p38α-dependent Bax activation in intestinal epithelial cells. These finding provide mechanistic insight into the role that EGFR signaling plays in the regulation of enterocyte apoptosis following massive intestinal loss. [ABSTRACT FROM AUTHOR]

Limited data in animal models suggest that colonic mucosa undergoes adaptive growth following massive small bowel resection (SBR). In vitro data suggest that intestinal cell growth is regulated by reactive oxygen species and redox couples [e.g., glutathione (GSH)/glutathione disulfide (GSSG) and cysteine (Cys)/cystine (CySS) redox]. We investigated the effects of SBR and alterations in redox on colonic growth indexes in rats after either small bowel transection (TX) or 80% midjejunoileal resection (RX). Rats were pair fed ± blockade of endogenous OSH synthesis with buthionine sulfoximine (BSO). Indexes of colonic growth, proliferation, and apoptosis and GSH/GSSG and Cys/CySS redox potentials (Eh) were determined. RX significantly increased colonic crypt depth, number of cells per crypt, and epithelial cell proliferation [crypt cell broniodeoxyuridine (BrdU) incorporation]. Administration of BSO markedly decreased colonic mucosal GSH, GSSG, and Cys concentrations in both TX and RX groups, with a resultant oxidation of GSH/GSSG and Cys/CySS Eh. BSO did not alter colonic crypt cell apoptosis but significantly increased all colonic mucosal growth indexes (crypt depth, cells/crypt, and BrdU incorporation) in both TX and RX groups in a time- and dose-dependent manner. BSO significantly decreased plasma GSH and GSSG, oxidized GSH/GSSG Eh, and increased plasma Cys and CySS concentrations. Collectively, these data provide in vivo evidence indicating that oxidized colonic mucosal redox status stimulates colonic mucosal growth in rats. The data also suggest that GSH is required to maintain normal colonic and plasma Cys/CySS homeostasis in these animal models. [ABSTRACT FROM AUTHOR]

Prior studies of intestinal adaptation after massive small bowel resection (SBR) have focused on growth factors and their effects on amplification of the gut mucosa. Because adaptive changes have also been described in intestinal smooth muscle, we sought to determine the effect of targeted smooth muscle growth factor overexpression on resectioninduced intestinal adaptation. Male transgenic mice with smooth muscle cell overexpression of insulin-like growth factor I (IGF-I) by virtue of an α-smooth muscle actin promoter were obtained. SMP8 IGF-I transgenic (IGF-I TG) and nontransgenic (NT) littermates underwent 50% proximal SBR or sham operation and were then killed after 3 or 28 days. NT mice showed the expected alterations in mucosal adaptive parameters after SBR, such as increased wet weight and villus height. The IGF-I TG mice had inherently taller villi, which did not increase significantly after SBR. In addition, IGF-I TG mice had a 50% postresection persistent increase in remnant intestinal length, which was associated with an early decline and later increase in relative mucosal surface area. These results indicate that growth factor overexpression within the muscularis layer of the bowel wall induces significant postresection adaptive intestinal lengthening and a unique mucosal response. IGF-I signaling within the muscle wall may play an important role in the pathogenesis of resection-induced adaptation. [ABSTRACT FROM AUTHOR]

Glucagon-like peptide-2 (GLP-2) is an intestinal trophic enteroendocrine peptide that is associated with intestinal adaptation following resection. Herein, we investigate the effects of GLP-2 in a total parenteral nutrition (TPN)-supported model of experimental short bowel syndrome. Juvenile Sprague-Dawley rats underwent a 90% small intestinal resection and jugular catheter insertion. Rats were randomized to three groups: enteral diet and intravenous saline infusion, TPN only, or TPN + 10 μg·kg-1·h -1 GLP-2. Nutritional maintenance was isocaloric and isonitrogenous. After 7 days, intestinal permeability was assessed by quantifying the urinary recovery of gavaged carbohydrate probes. The following day, animals were euthanized, and intestinal tissue was processed for morphological and crypt cell proliferation (CCP) analysis, apoptosis (caspase-3), and expression of SGLT-1 and GLUT-5 transport proteins. TPN plus GLP-2 treatment resulted in increased bowel and body weight, villus height, intestinal mucosal surface area, CCP, and reduced intestinal permeability compared with the TPN alone animals (P < 0.05). GLP-2 treatment induced increases in serum GLP-2 levels and intestinal SGLT-1 expression (P < 0.01) compared with either TPN or enteral groups. No differences were seen in the villus apoptotic index between resection groups. Enterally fed resected animals had a significant decrease in crypt apoptotic indexes compared with nontreated animals. This study demonstrates that GLP-2 alone, without enteral feeding, stimulates indexes of intestinal adaptation. Secondly, villus hypertrophy associated with adaptation was predominantly due to an increase in CCP and not to changes in apoptotic rates. Further studies are warranted to establish the mechanisms of action and therapeutic potential of GLP-2. [ABSTRACT FROM AUTHOR]

Mortality associated with liver disease has been observed in patients with short bowel syndrome (SBS); however, its mechanism remains unclear, but bile acid (BA) dysmetabolism has been proposed as a possible cause. The farnesoid X receptor (FXR) is the key regulator of BA synthesis. Here, we showed that, in a rat model of short bowel resection associated with liver disease (SBR-ALD), the BA composition of hepatic tissues reflected a larger proportion of primary and secondary unconjugated BAs, whereas that of the colon contents and serum showed an increased ratio of secondary unconjugated BAs. Both hepatic and intestinal regulation of BA synthesis was characterized by a blunted hepatic FXR activation response. The mRNA expression levels of cholesterol 7a-hydroxylase ( CYP7A1 ), sterol 12a-hydroxylase ( CYP8B1 ), and sterol 27 hydroxylase ( CYP27A1 ), the key enzymes in BA synthesis, were upregulated. After intervention with the FXR agonist GW4064, both the liver histology and serum transaminase activity were improved, which demonstrated the attenuation of SBR-ALD. The BA compositions of hepatic tissue, the colon contents, and serum recovered and were closer to those of the sham group. The expression levels of hepatic FXR increased, and its target genes were activated. Consistent with this, the expression levels of CYP7A1 , CYP8B1 , and CYP27A1 were downregulated. Ileum tissue FXR and its target genes were slightly elevated. This study showed that the FXR agonist GW4064 could correct BA dysmetabolism to alleviate hepatotoxicity in SBR animals. GW4064 intervention resulted in a decrease in fecal bile excretion and elevated plasma/hepatic conjugated BA levels. GW4064 increased the reabsorption of conjugated BAs by inducing apical sodium-dependent bile salt transporter expression in the ileum. Concomitantly, FXR activation in the presence of GW4064 decreased BA production by repressing the expression of key synthetases, including CYP7A1 , CYP8B1 , and CYP27A1 . These findings provide a clinical research direction for the prevention of liver disease in patients with SBS. NEW & NOTEWORTHY This study assessed the impact of treatment with GW4064, a farnesoid X receptor agonist, on the development of short bowel resection (SBR) associated with liver disease in a rat model of SBR. GW4064 was able to correct bile acid dysmetabolism and alleviate hepatotoxicity in SBR animals.

Enteroendocrine L cells and glucagon-like peptide 2 (GLP-2) secretion are activated in the intestinal adaptation process following bowel resection in patients with short bowel syndrome. We hypothesized that enteral activation of Takeda G protein-coupled receptor 5 (TGR5), expressed in enteroendocrine L cells, could augment endogenous GLP-2 secretion and the intestinal adaptation response. Our aim was to assess the efficacy of different TGR5 agonists to stimulate GLP-2 secretion and intestinal adaptation in a piglet short-bowel model. In study 1 , parenterally fed neonatal pigs ( n = 6/group) were gavaged with vehicle, olive extract (OE; 10 or 50 mg/kg), or ursolic acid (UA; 10 mg/kg), and plasma GLP-2 was measured for 6 h. In study 2 , neonatal pigs ( n = 6-8/group) were subjected to transection or 80% mid-small intestine resection and, after 2 days, assigned to treatments for 10 days as follows: 1 ) transection + vehicle (sham), 2 ) resection + vehicle (SBS), 3 ) resection + 30 mg UA (SBS + UA), and 4 ) resection + 180 mg/kg OE (SBS + OE). We measured plasma GLP-2, intestinal histology, cell proliferation, and gene expression, as well as whole body citrulline-arginine kinetics and bile acid profiles. In study 1 , GLP-2 secretion was increased by UA and tended to be increased by OE. In study 2 , SBS alone, but not additional treatment with either TGR5 agonist, resulted in increased mucosal thickness and crypt cell proliferation in remnant jejunum and ileum sections. SBS increased biliary and ileal concentration of bile acids and expression of inflammatory and farnesoid X receptor target genes, but these measures were suppressed by UA treatment. In conclusion, UA is an effective oral GLP-2 secretagogue in parenterally fed pigs but is not capable of augmenting GLP-2 secretion or the intestinal adaptation response after massive small bowel resection. NEW & NOTEWORTHY Therapeutic activation of endogenous glucagon-like peptide 2 (GLP-2) secretion is a promising strategy to improve intestinal adaptation in patients with short bowel syndrome. This study in neonatal pigs showed that oral supplementation with a selective Takeda G protein-coupled receptor 5 (TGR5) agonist is an effective approach to increase GLP-2 secretion. The results warrant further study to establish a more potent oral TGR5 agonist that can effectively improve intestinal adaptation in pediatric patients with SBS.