Alteration in epithelial permeability and ion transport in a mouse model of total parenteral nutrition

Nutrition and the gut-brain axis in neonatal brain injury and development

Early nutritional exposures, including during embryogenesis and the immediate postnatal period, affect offspring outcomes in both the short- and long-term. Alterations of these modifiable exposures shape the developing gut microbiome, intestinal development, and even neurodevelopmental outcomes. A gut-brain axis exists, and it is intricately connected to early life feeding and nutritional exposures. Here, we seek to discuss the (1) origins of the gut-brain access and relationship with neurodevelopment, (2) components of human milk (HM) beyond nutrition and their role in the developing newborn, and (3) clinical application of nutritional practices, including fluid management and feeding on the development of the gut-brain axis, and long-term neurodevelopmental outcomes. We conclude with a discussion on future directions and unanswered questions that are critical to provide further understanding and insight into how clinicians and healthcare providers can optimize early nutritional practices to ensure children not only survive, but thrive, free of neurodevelopmental impairment.

Parenteral Nutrition, Inflammatory Bowel Disease, and Gut Barrier: An Intricate Plot

Malnutrition poses a critical challenge in inflammatory bowel disease, with the potential to detrimentally impact medical treatment, surgical outcomes, and general well-being. Parenteral nutrition is crucial in certain clinical scenarios, such as with patients suffering from short bowel syndrome, intestinal insufficiency, high-yielding gastrointestinal fistula, or complete small bowel obstruction, to effectively manage malnutrition. Nevertheless, research over the years has attempted to define the potential effects of parenteral nutrition on the intestinal barrier and the composition of the gut microbiota. In this narrative review, we have gathered and analyzed findings from both preclinical and clinical studies on this topic. Based on existing evidence, there is a clear correlation between short- and long-term parenteral nutrition and negative effects on the intestinal system. These include mucosal atrophic damage and immunological and neuroendocrine dysregulation, as well as alterations in gut barrier permeability and microbiota composition. However, the mechanistic role of these changes in inflammatory bowel disease remains unclear. Therefore, further research is necessary to effectively address the numerous gaps and unanswered questions pertaining to these issues.

Epigallocatechin gallate as a nutraceutical to potentially target the metabolic syndrome: novel insights into therapeutic effects beyond its antioxidant and anti-inflammatory properties

Epigallocatechin gallate (EGCG) is one of the most abundant and powerful flavonoids contained in green tea. Because of the global increase in green tea consumption, there has been a general interest in understanding its health benefits, including its bioactive compounds like EGCG. Indeed, preclinical evidence already indicates that EGCG demonstrated a strong antioxidant and anti-inflammatory properties that could be essential in protecting against metabolic syndrome. The current review explores clinical evidence reporting on the beneficial effects of EGCG supplementation in obese subjects or patients with diverse metabolic complications that include type 2 diabetes and cardiovascular disease. The discussion incorporates the impact of different formulations of EGCG, as well as the effective doses and treatment duration. Importantly, besides highlighting the potential use of EGCG as a nutraceutical, the current review also discusses crucial evidence related to its pharmaceutical development as an agent to hinder metabolic diseases, including its bioavailability and metabolism profile, as well as its well-known biological properties.

Role of the Gut Microbiota in Parenteral Nutrition-Associated Liver Disease: From Current Knowledge to Future Opportunities

Parenteral nutrition-associated liver disease (PNALD) refers to a spectrum of conditions that can develop cholestasis, steatosis, fibrosis, and cirrhosis in the setting of parenteral nutrition (PN) use. Patient risk factors include short bowel syndrome, bacterial overgrowth and translocation, disturbance of hepatobiliary circulation, and lack of enteral feeding. A growing body of evidence suggests an intricate linkage between the gut microbiota and the pathogenesis of PNALD. In this review, we highlight current knowledge on the taxonomic and functional changes in the gut microbiota that might serve as noninvasive biomarkers. We also discuss the function of microbial metabolites and associated signaling pathways in the pathogenesis of PNALD. By providing the perspectives of microbiota-host interactions in PNALD for basic and translational research and summarizing current limitations of microbiota-based approaches, this review paves the path for developing novel and precise microbiota-based therapies in PNALD.

Models to evaluate the barrier properties of mucus during drug diffusion

Mucus is widely disseminated in the nasal cavity, oral cavity, respiratory tract, eyes, gastrointestinal tract, and reproductive tract to prevent the invasion of pathogenic bacteria and toxins. The mucus layer through its continuous secretion can prevent the passage of macromolecular substances such as pathogenic bacteria and toxins, thereby reducing the occurrence of inflammation. Without a doubt, mucus also hinders oral absorption. The physiological and biochemical properties of intestinal mucus and the different types of mucus barrier models need to be predominated. To find ways to increase the bioavailability of drugs in the future, this article summarizes mucus composition, barrier properties, mucus models, and mucoadhesive/mucopenetrating particles to highlight the information they can afford. Collectively, the review seeks to provide a state-of-the-art roadmap for researchers who must contend with this critical barrier to drug delivery.

Nano- and micro-particles for delivery of catechins: Physical and biological performance

Catechins, present in many fruits and vegetables, have many health benefits, but they are prone to degradation. Nano- and micro-particle systems have been used to stabilise catechins when exposed to adverse environments and to improve their bioavailability after ingestion. This review discusses the inherent properties of various catechins, the design of delivery formulations and the properties of catechin-loaded nano- and micro-particles. The protection afforded to catechins during exposure to harsh environmental conditions and gastrointestinal tract transit is reviewed. The bioavailability and efficacy of encapsulated catechins, as assessed by various in vitro and in vivo conditions, are discussed. Bioavailability based on uptake in the upper gut alone underestimates the bioavailability as polyphenols. The caveats with interpretation of bioavailability based on various tests are discussed, when taking into consideration the pathways of catechin metabolism including the role of the gut microflora. However, taken together, the weight of the evidence suggests that there are potentially improved health benefits with the use of appropriately designed nano- and micro-particles for delivery of catechins. Further systematic studies on the metabolism and physiological effects of encapsulated catechins in vivo and clinical trials are needed to validate the bioefficacy of the encapsulated catechins.

P38 MAPK Pharmacological Inhibitor SB203580 Alleviates Total Parenteral Nutrition-Induced Loss of Intestinal Barrier Function but Promotes Hepatocyte Lipoapoptosis

BACKGROUND & AIMS

Our previous studies have provided evidence that p38 mitogen-activated protein kinase (MAPK) is involved in total parenteral nutrition (TPN)-associated complications, but its exact effects and mechanisms have not been fully understood. This study aimed to evaluate the roles of p38 MAPK inhibitor SB203580 in the TPN-induced loss of intestinal barrier function and liver disease.

METHODS

A rodent model of TPN was used to analyze the roles of SB203580 in TPN-associated complications.Intestinal barrier function was evaluated by transepithelial electrical resistance (TER) and paracellular permeability in Caco-2 cells. The palmitic acid (PA) was used to induce hepatic lipoapoptosis in vitro. The lipoapoptosis was detected using Caspase-3/7 and lipid staining.

RESULTS

In the present study, we showed that SB203580 treatment significantly suppressed TPN-mediated intestinal permeability in rats. SB203580 treatment significantly inhibited IL-1β-induced an increase in tight junction permeability of Caco-2 cells via repressing the p38/ATF-2 signaling. Unexpectedly, SB203580 treatment enhanced hepatic lipoapoptosis in the model of TPN. Palmitic acid (PA)-induced hepatic lipoapoptosis in human liver cells was significantly augmented by the SB203580 treatment.

CONCLUSIONS

We demonstrate that the p38 MAPK inhibitor SB203508 ameliorates intestinal barrier function but promotes hepatic lipoapoptosis in model of TPN.

Bombesin Prevents the Atrophy of Peyer's Patches and the Dysfunction of M Cells in Rabbits Receiving Long-Term Parenteral Nutrition

BACKGROUND

Long-term parenteral nutrition (PN) induces atrophy of the gut-associated lymphoid tissue (GALT). We examined whether bombesin could ameliorate this atrophy of Peyer's patches and the down-regulation of particle transport by M cells, which was also observed in rabbits undergoing PN.

METHODS

Adult female rabbits were randomized into 6 groups to receive chow ad libitum, chow + bombesin, PN, or PN + bombesin (20 microg/kg, subcutaneously every 8 hours) for 2 or 4 weeks. At the end of each nutrition period, a laparotomy was performed under anesthesia and a suspension of 1 x 10(10)/mL of 0.5-microm fluorescent microspheres was injected into the lumen of intestinal segments containing Peyer's patches and incubated for 2 hours. After the incubation, segments were harvested and prepared for light microscopy, immunohistochemistry, fluorescent microscopy, and electron microscopy.

RESULTS

Long-term PN reduced the size of ileal Peyer's patches, the number of microspheres that was taken up into the follicle-associated epithelium of lymphoid nodules, and the area of Peyer's patch surface occupied by M cells. The number of intraepithelial lymphocytes within the follicle-associated epithelium near the perifollicular crypts of Peyer's patches was also reduced by long-term PN. These consequences were dramatically ameliorated by treatment with bombesin. No ultrastructural alteration of the M cells of Peyer's patches was found in the chow, the PN, or the PN + bombesin groups.

CONCLUSIONS

Bombesin prevents PN-induced atrophy of GALT, reduction of M cell numbers, and decrease in particulate transport by M cells during long-term PN. Bombesin may modulate the genesis of and particulate transport by M cells through stimulation of lymphoid cells in Peyer's patch epithelium near perifollicular crypts, where M cells and other constituents of lymphoid follicle epithelium are generated, thereby preserving mucosal immunity.

Gastrointestinal transport of calcium and glucose in lactating ewes

During lactation, mineral and nutrient requirements increase dramatically, particularly those for Ca and glucose. In contrast to monogastric species, in ruminants, it is rather unclear to which extend this physiological change due to increased demand for milk production is accompanied by functional adaptations of the gastrointestinal tract (GIT). Therefore, we investigated potential modulations of Ca and glucose transport mechanisms in the GIT of lactating and dried‐off sheep. Ussing‐chamber technique was applied to determine the ruminal and jejunal Ca flux rates. In the jejunum, electrophysiological properties in response to glucose were recorded. Jejunal brush‐border membrane vesicles (BBMV) served to characterize glucose uptake via sodium‐linked glucose transporter 1 (SGLT1), and RNA and protein expression levels of Ca and glucose transporting systems were determined. Ruminal Ca flux rate data showed a trend for higher absorption in lactating sheep. In the jejunum, small Ca absorption could only be observed in lactating ewes. From the results, it may be assumed that lactating ewes compensate for the Ca loss by increasing bone mobilization rather than by increasing supply through absorption from the GIT. Presence of SGLT1 in the jejunum of both groups was shown by RNA and protein identification, but glucose uptake into BBMV could only be detected in lactating sheep. This, however, could not be attributed to electrogenic glucose absorption in lactating sheep under Ussing‐chamber conditions, providing evidence that changes in jejunal glucose uptake may include additional factors, that is, posttranslational modifications such as phosphorylation.

Bacterial nutrient foraging in a mouse model of enteral nutrient deprivation: insight into the gut origin of sepsis

Total parenteral nutrition (TPN) leads to a shift in small intestinal microbiota with a characteristic dominance of Proteobacteria This study examined how metabolomic changes within the small bowel support an altered microbial community in enterally deprived mice. C57BL/6 mice were given TPN or enteral chow. Metabolomic analysis of jejunal contents was performed by liquid chromatography/mass spectrometry (LC/MS). In some experiments, leucine in TPN was partly substituted with [¹³C]leucine. Additionally, jejunal contents from TPN-dependent and enterally fed mice were gavaged into germ-free mice to reveal whether the TPN phenotype was transferrable. Small bowel contents of TPN mice maintained an amino acid composition similar to that of the TPN solution. Mass spectrometry analysis of small bowel contents of TPN-dependent mice showed increased concentration of ¹³C compared with fed mice receiving saline enriched with [¹³C]leucine. [¹³C]leucine added to the serosal side of Ussing chambers showed rapid permeation across TPN-dependent jejunum, suggesting increased transmucosal passage. Single-cell analysis by fluorescence in situ hybridization (FISH)-NanoSIMS demonstrated uptake of [¹³C]leucine by TPN-associated bacteria, with preferential uptake by Enterobacteriaceae Gavage of small bowel effluent from TPN mice into germ-free, fed mice resulted in a trend toward the proinflammatory TPN phenotype with loss of epithelial barrier function. TPN dependence leads to increased permeation of TPN-derived nutrients into the small intestinal lumen, where they are predominately utilized by Enterobacteriaceae The altered metabolomic composition of the intestinal lumen during TPN promotes dysbiosis.

Early enteral nutrition improves intestinal immune barrier in a rat model of severe acute pancreatitis

BACKGROUND

The aim of the present study was to investigate the role of early enteral nutrition (EEN) in the intestinal immune barrier in severe acute pancreatitis (SAP), and to explore its potential mechanisms.

METHODS

Sixty rats were randomly assigned to three groups: sham-operated group (SO group, n = 20), SAP group receiving EEN (SAP + EEN group, n = 20), and SAP group receiving total parental nutrition (SAP + TPN group, n = 20). SAP was induced by infusion of sodium taurocholate. Rats were killed 5 days after nutritional support. The pathological damage of the intestine was determined using HE staining. The expression of MAdCAM-1, CD⁴⁺ , and CD⁸⁺ in Peyer's lymph nodes of the distal ilium was examined by immunohistochemistry. Serum levels of endotoxin and bacterial translocation were determined.

RESULTS

The survival rate in the SAP + TPN (50%) and SAP + EEN (75%) groups was significantly lower than in the SO group (100%) (P < 0.05). The survival rate in the SAP + EEN group was significantly higher than in the SAP + TPN group (P < 0.05). The expression of MAdCAM-1, CD⁴⁺ and CD⁸⁺ in the intestine was decreased in SAP rats. EEN significantly increased the expression of MAdCAM-1, CD⁴⁺ and CD⁸⁺ compared with TPN, accompanied by a decrease in the serum levels of endotoxin and bacterial translocation.

CONCLUSIONS

Early enteral nutrition improves intestinal immune barrier, thus reducing bacterial and endotoxin translocation and improving the survival rate in SAP rats.

Tight Junction Ultrastructure Alterations in a Mouse Model of Enteral Nutrient Deprivation

BACKGROUND

Total parenteral nutrition (TPN), a necessary treatment for patients who cannot receive enteral nutrition, is associated with infectious complications due in part to a loss of intestinal epithelial barrier function (EBF). Using a mouse model of TPN, with enteral nutrient deprivation, we previously demonstrated an increase in mucosal interferon-γ and tumor necrosis factor-α; these cytokine changes are a major mediator driving a reduction in epithelial tight junction (TJ) protein expression. However, the exact ultrastructural changes to the intestinal epithelial barrier have not been previously described.

AIM

We hypothesized that TPN dependence results in ultrastructural changes in the intestinal epithelial TJ meshwork.

METHODS

C57BL/6 mice underwent internal jugular venous cannulation and were given enteral nutrition or TPN with enteral nutrient deprivation for 7 days. Freeze-fracture electron microscopy was performed on ileal tissue to characterize changes in TJ ultrastructure. EBF was measured using transepithelial resistance and tracer permeability, while TJ expression was measured via Western immunoblotting and immunofluorescence staining.

RESULTS

While strand density, linearity, and appearance were unchanged, TPN dependence led to a mean reduction in one horizontal strand out of the TJ compact meshwork to a more basal region, resulting in a reduction in meshwork depth. These findings were correlated with the loss of TJ localization of claudin-4 and tricellulin, reduced expression of claudin-5 and claudin-8, and reduced ex vivo EBF.

CONCLUSION

Tight junction ultrastructural changes may contribute to reduced EBF in the setting of TPN dependence.

Changes to the Intestinal Microbiome With Parenteral Nutrition: Review of a Murine Model and Potential Clinical Implications

Parenteral nutrition (PN) dependence, while life sustaining, carries a significant risk of septic complications associated with epithelial barrier dysfunction and translocation of gut-derived microbiota. Increasing evidence suggests that PN-associated changes in the intestinal microbiota play a central role in the breakdown of the intestinal epithelial barrier. This review outlines the clinical and experimental evidence of epithelial barrier dysfunction with PN, the role of gut inflammatory dysregulation in driving this process, and the role of the intestinal microbiome in modulating inflammation in the gut and systemically. The article summarizes the most current work of our laboratory and others and describes many of the laboratory findings behind our current understanding of the PN enteral environment. Understanding the interaction between nutrient delivery, the intestinal microbiome, and PN-associated complications may lead to the development of novel therapies to enhance safety and quality of life for patients requiring PN.

Gut Microbiota and Immunity: Possible Role in Sudden Infant Death Syndrome

The gut microbiome influences the development of the immune system of young mammals; the establishment of a normal gut microbiome is thought to be important for the health of the infant during its early development. As the role of bacteria in the causation of sudden infant death syndrome (SIDS) is backed by strong evidence, the balance between host immunity and potential bacterial pathogens is likely to be pivotal. Bacterial colonization of the infant colon is influenced by age, mode of delivery, diet, environment, and antibiotic exposure. The gut microbiome influences several systems including gut integrity and development of the immune system; therefore, gut microflora could be important in protection against bacteria and/or their toxins identified in SIDS infants. The aims of the review are to explore (1) the role of the gut microbiome in relation to the developmentally critical period in which most SIDS cases occur; (2) the mechanisms by which the gut microbiome might induce inflammation resulting in transit of bacteria from the lumen into the bloodstream; and (3) assessment of the clinical, physiological, pathological, and microbiological evidence for bacteremia leading to the final events in SIDS pathogenesis.

Loss of ileum decreases serum fibroblast growth factor 19 in relation to liver inflammation and fibrosis in pediatric onset intestinal failure

BACKGROUND & AIMS

The pathogenesis of intestinal failure (IF) associated liver disease (IFALD) is uncertain, we therefore investigated the role of FGF19 and pro-inflammatory cytokines has on this disease state.

METHODS

Serum FGF19, IL-6 and, TNF-α were measured in 52 IF patients at median age 6.0 years (IQR 2.2-13) after 10 months (4.1-39) on parenteral nutrition (PN). Thirty-nine patients underwent liver biopsies.

RESULTS

In IF patients, FGF19 concentrations were lower and those of IL-6 and TNF-α higher compared to healthy matched controls (p ⩽ 0.001 for all). FGF19 concentrations were further decreased in patients without a remaining ileum [37 pg/ml (IQR 30-68) vs. 74 (35-135) p=0.028], and correlated with remaining ileum length (r = 0.333, p = 0.018) and markers of cholesterol synthesis (r = -0.552 to -0.643, p < 0.001). Patients with histological portal inflammation [30 pg/ml (28-45) vs. 48 (33-100), p = 0.019] or fibrosis [35 pg/ml (30-66) vs. 99 (38-163), p = 0.013] had lower serum FGF19 concentrations than others. FGF19 negatively correlated with portal inflammation grade (r = -0.442, p = 0.005), serum TNF-α (r = -0.318, p = 0.025), METAVIR fibrosis stage (r = -0.441, p = 0.005) and APRI (r = -0.328, p = 0.028). IL-6 was higher during PN [6 pg/ml (2-31)] than after weaning off PN [2 pg/ml (1-5), p = 0.009], correlated weakly with cholestasis grade (r = 0.328, p = 0.044), and tended to associate with histological cholestasis [n = 5, 5 pg/ml (5-267) vs. n=34, 2 pg/ml (1-7), p = 0.058].

CONCLUSIONS

In pediatric onset of IF, total or partial loss of ileum decreases serum FGF19 concentration corresponding to hepatic inflammation and fibrosis, along with increased cholesterol synthesis. In contrast, serum IL-6 increases during PN and may associate with concurrent cholestasis. These data suggests that FGF19 may contribute to the pathogenesis of IFALD.

Choline Alleviates Parenteral Nutrition-Associated Duodenal Motility Disorder in Infant Rats

BACKGROUND

Parenteral nutrition (PN) has been found to influence duodenal motility in animals. Choline is an essential nutrient, and its deficiency is related to PN-associated organ diseases. Therefore, this study was aimed to investigate the role of choline supplementation in an infant rat model of PN-associated duodenal motility disorder.

MATERIALS AND METHODS

Three-week-old Sprague-Dawley male rats were fed chow and water (controls), PN solution (PN), or PN plus intravenous choline (600 mg/kg) (PN + choline). Rats underwent jugular vein cannulation for infusion of PN solution or 0.9% saline (controls) for 7 days. Duodenal oxidative stress status, concentrations of plasma choline, phosphocholine, and betaine and serum tumor necrosis factor (TNF)-α were assayed. The messenger RNA (mRNA) and protein expression of c-Kit proto-oncogene protein (c-Kit) and membrane-bound stem cell factor (mSCF) together with the electrophysiological features of slow waves in the duodenum were also evaluated.

RESULTS

Rats on PN showed increased reactive oxygen species; decreased total antioxidant capacity in the duodenum; reduced plasma choline, phosphocholine, and betaine; and enhanced serum TNF-α concentrations, which were reversed by choline intervention. In addition, PN reduced mRNA and protein expression of mSCF and c-Kit, which were inversed under choline administration. Moreover, choline attenuated depolarized resting membrane potential and declined the frequency and amplitude of slow waves in duodenal smooth muscles of infant rats induced by PN, respectively.

CONCLUSION

The addition of choline to PN may alleviate the progression of duodenal motor disorder through protecting smooth muscle cells from injury, promoting mSCF/c-Kit signaling, and attenuating impairment of interstitial cells of Cajal in the duodenum during PN feeding.

Enteral nutrient deprivation in patients leads to a loss of intestinal epithelial barrier function

OBJECTIVE

To investigate the effect of nutrient withdrawal on human intestinal epithelial barrier function (EBF). We hypothesized that unfed mucosa results in decreased EBF. This was tested in a series of surgical small intestinal resection specimens.

DESIGN

Small bowel specifically excluding inflamed tissue, was obtained from pediatric patients (aged 2 days to 19 years) undergoing intestinal resection. EBF was assessed in Ussing chambers for transepithelial resistance (TER) and passage of fluorescein isothiocyanate (FITC)-dextran (4 kD). Tight junction and adherence junction proteins were imaged with immunofluorescence staining. Expression of Toll-like receptors (TLR) and inflammatory cytokines were measured in loop ileostomy takedowns in a second group of patients.

RESULTS

Because TER increased with patient age (P < .01), results were stratified into infant versus teenage groups. Fed bowel had significantly greater TER versus unfed bowel (P < .05) in both age populations. Loss of EBF was also observed by an increase in FITC-dextran permeation in enteral nutrient-deprived segments (P < .05). Immunofluorescence staining showed marked declines in intensity of ZO-1, occludin, E-cadherin, and claudin-4 in unfed intestinal segments, as well as a loss of structural formation of tight junctions. Analysis of cytokine and TLR expression showed significant increases in tumor necrosis factor (TNF)-α and TLR4 in unfed segments of bowel compared with fed segments from the same individual.

CONCLUSION

EBF declined in unfed segments of human small bowel. This work represents the first direct examination of EBF from small bowel derived from nutrient-deprived humans and may explain the increased incidence of infectious complications seen in patients not receiving enteral feeds.

Stimulation of intestinal growth and function with DPP4 inhibition in a mouse short bowel syndrome model

Glucagon-like 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-week-old 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.

Phytosterols promote liver injury and Kupffer cell activation in parenteral nutrition-associated liver disease

Parenteral nutrition-associated liver disease (PNALD) is a serious complication of PN in infants who do not tolerate enteral feedings, especially those with acquired or congenital intestinal diseases. Yet, the mechanisms underlying PNALD are poorly understood. It has been suggested that a component of soy oil (SO) lipid emulsions in PN solutions, such as plant sterols (phytosterols), may be responsible for PNALD, and that use of fish oil (FO)-based lipid emulsions may be protective. We used a mouse model of PNALD combining PN infusion with intestinal injury to demonstrate that SO-based PN solution causes liver damage and hepatic macrophage activation and that PN solutions that are FO-based or devoid of all lipids prevent these processes. We have furthermore demonstrated that a factor in the SO lipid emulsions, stigmasterol, promotes cholestasis, liver injury, and liver macrophage activation in this model and that this effect may be mediated through suppression of canalicular bile transporter expression (Abcb11/BSEP, Abcc2/MRP2) via antagonism of the nuclear receptors Fxr and Lxr, and failure of up-regulation of the hepatic sterol exporters (Abcg5/g8/ABCG5/8). This study provides experimental evidence that plant sterols in lipid emulsions are a major factor responsible for PNALD and that the absence or reduction of plant sterols is one of the mechanisms for hepatic protection in infants receiving FO-based PN or lipid minimization PN treatment. Modification of lipid constituents in PN solutions is thus a promising strategy to reduce incidence and severity of PNALD.

Proceedings of the 2013 A.S.P.E.N. Research workshop: the interface between nutrition and the gut microbiome: implications and applications for human health [corrected]

The human and earth microbiomes are among the most important biological agents in understanding and preventing disease. Technology is advancing at a fast pace and allowing for high-resolution analysis of the composition and function of our microbial partners across regions, space, and time. Bioinformaticists and biostatisticians are developing ever more elegant displays to understand the generated megadatasets. A virtual cyberinfrastructure of search engines to cross-reference the rapidly developing data is emerging in line with technologic advances. Nutrition science will reap the benefits of this new field, and its role in preserving the earth and the humans who inhabit it will become evidently clear. In this report we highlight some of the topics of an A.S.P.E.N.-sponsored symposium held during Clinical Nutrition Week in 2013 that address the importance of the human microbiome to human health and disease.

Intestinal epithelial cell apoptosis and loss of barrier function in the setting of altered microbiota with enteral nutrient deprivation

Total parenteral nutrition (TPN), a commonly used treatment for patients who cannot receive enteral nutrition, is associated with significant septic complications due in part to a loss of epithelial barrier function (EBF). While the underlying mechanisms of TPN-related epithelial changes are poorly understood, a mouse model of TPN-dependence has helped identify several contributing factors. Enteral deprivation leads to a shift in intestinal microbiota to predominantly Gram-negative Proteobacteria. This is associated with an increase in expression of proinflammatory cytokines within the mucosa, including interferon-γ and tumor necrosis factor-α. A concomitant loss of epithelial growth factors leads to a decrease in epithelial cell proliferation and increased apoptosis. The resulting loss of epithelial tight junction proteins contributes to EBF dysfunction. These mechanisms identify potential strategies of protecting against TPN-related complications, such as modification of luminal bacteria, blockade of proinflammatory cytokines, or growth factor replacement.

Regulation of epithelial differentiation in rat intestine by intraluminal delivery of an adenoviral vector or silencing RNA coding for Schlafen 3

Although we stimulate enterocytic proliferation to ameliorate short gut syndrome or mucosal atrophy, less effort has been directed at enterocytic differentiation. Schlafen 3 (Slfn3) is a poorly understood protein induced during IEC-6 enterocytic differentiation. We hypothesized that exogenous manipulation of Slfn3 would regulate enterocytic differentiation in vivo. Adenoviral vector coding for Slfn3 cDNA (Ad-GFP-Slfn3) or silencing RNA for Slfn3 (siSlfn3) was introduced intraluminally into rat intestine. We assessed Slfn3, villin, sucrase-isomaltase (SI), Dpp4, and Glut2 by qRT-PCR, Western blot, and immunohistochemistry. We also studied Slfn3 and these differentiation markers in atrophic defunctionalized jejunal mucosa and the crypt-villus axis of normal jejunum. Ad-GFP-Slfn3 but not Ad-GFP increased Slfn3, villin and Dpp4 expression in human Caco-2 intestinal epithelial cells. Injecting Ad-GFP-Slfn3 into rat jejunum in vivo increased mucosal Slfn3 mRNA three days later vs. intraluminal Ad-GFP. This Slfn3 overexpression was associated with increases in all four differentiation markers. Injecting siSlfn3 into rat jejunum in vivo substantially reduced Slfn3 and all four intestinal mucosal differentiation markers three days later, as well as Dpp4 specific activity. Endogenous Slfn3 was reduced in atrophic mucosa from a blind-end Roux-en-Y anastomosis in parallel with differentiation marker expression together with AKT and p38 signaling. Slfn3 was more highly expressed in the villi than the crypts, paralleling Glut2, SI and Dpp4. Slfn3 is a key intracellular regulator of rat enterocytic differentiation. Understanding how Slfn3 works may identify targets to promote enterocytic differentiation and maintain mucosal function in vivo, facilitating enteral nutrition and improving survival in patients with mucosal atrophy or short gut syndrome.

Angiotensin converting enzyme-inhibitor reduces colitis severity in an IL-10 knockout model

BACKGROUND

We previously demonstrated angiotensin converting enzymes (ACE) over-expression in a dextran-sodium sulfate colitis model; ACE inhibitor (ACE-I) treatment reduced colitis severity in this model. However, ACE-I has not been tested in more immunologically relevant colitis models.

AIM

We hypothesized that ACE-I would decrease disease severity in an IL-10 knockout (-/-) colitis model.

METHODS

Colitis was induced by giving 10-week old IL-10-/- mice piroxicam (P.O.) for 14 days. The ACE-I enalaprilat was given transanally at a dose of 6.25 mg/kg for 21 days. Prednisolone (PSL) with or without enalaprilat were used as therapeutic, comparative groups. All groups were compared to a placebo treated group. Outcome measures were clinical course, histology, abundance of pro-inflammatory cytokines/chemokines, and epithelial barrier function.

RESULTS

Enalaprilat exhibited better survival (91 %) versus other treatment groups (PSL: 85.7 %, PSL + ACE-I: 71.4 %, placebo: 66.6 %). The ACE-I and PSL + ACE-I groups showed significantly better histological scores versus placebo mice. ACE-I and the PSL groups significantly reduced several pro-inflammatory cytokines versus placebo mice. FITC-dextran permeability was reduced in the ACE-I and PSL + ACE-I groups. Blood pressure was not affected in ACE-I treated mice compared to placebo mice.

CONCLUSIONS

ACE-I was effective in reducing severity of colitis in an IL-10-/- model. The addition of prednisolone minimally augmented this effect. The findings suggest that appropriately dosed ACE-I with or without steroids may be a new therapeutic agent for colitis.

Disturbance of intraepithelial lymphocytes in a murine model of acute intestinal ischemia/reperfusion

Strategically located at the epithelial basolateral surface, intraepithelial lymphocytes (IELs) are intimately associated with epithelial cells and maintain the epithelial barrier integrity. Intestinal ischemia-reperfusion (I/R)-induced acute injury not only damages the epithelium but also affects the mucosal barrier function. Therefore, we hypothesized that I/R-induced mucosal damage would affect IEL phenotype and function. Adult C57BL/6J mice were treated with intestinal I/R or sham. Mice were euthanized at 6 h after I/R, and the small bowel was harvested for histological examination and to calculate the transmembrane resistance. Occludin expression and IEL location were detected through immunohistochemistry. The IEL phenotype, activation, and apoptosis were examined using flow cytometry. Cytokine and anti-apoptosis-associated gene expressions were measured through RT-PCR. Intestinal I/R induced the destruction of epithelial cells and intercellular molecules (occludin), resulting in IEL detachment from the epithelium. I/R also significantly increased the CD8αβ, CD4, and TCRαβ IEL subpopulations and significantly changed IEL-derived cytokine expression. Furthermore, I/R enhanced activation and promoted apoptosis in IELs. I/R-induced acute intestinal mucosal damage significantly affected IEL phenotype and function. These findings provide profound insight into potential IEL-mediated epithelial barrier dysfunction after intestinal I/R.

Persistent abnormal liver fibrosis after weaning off parenteral nutrition in pediatric intestinal failure

The aim of this study was to evaluate the long-term effects of pediatric intestinal failure (IF) on liver histology. Altogether, 38 IF patients (median age: 7.2 years; range, 0.2-27) underwent liver biopsy, gastroscopy, abdominal ultrasound, and laboratory tests. Sixteen patients were on parenteral nutrition (PN) after 74 PN months (range, 2.5-204). Twenty-two had weaned off PN 8.8 years (range, 0.3-27) earlier, after 35 PN months (range, 0.7-250). Fifteen transplant donor livers served as controls. Abnormal liver histology was found in 94% of patients on PN and 77% of patients weaned off PN (P = 0.370). During PN, liver histology weighted with cholestasis (38% of patients on PN versus 0% of patients weaned off PN; P = 0.003) and portal inflammation (38% versus 9%; P = 0.050) were found. Fibrosis (88% versus 64%; P = 0.143; Metavir stage: 1.6 [range, 0-4] versus 1.1 [range, 0-2]; P = 0.089) and steatosis (50% versus 45%; P = 1.000) were equally common during and after weaning off PN. Plasma alanine aminotransferase (78 U/L [range, 19-204] versus 34 [range, 9-129]; P = 0.009) and conjugated bilirubin (43 μmol/L [range, 1-215] versus 4 [range, 1-23]; P = 0.037) were significantly higher during than after weaning off PN. Esophageal varices were encountered in 1 patient after weaning off PN. Metavir stage was associated with small bowel length (r = -0.486; P = 0.002) and number of septic episodes (r = 0.480; P = 0.002). In a multivariate analysis, age-adjusted small bowel length (ß = -0.533; P = 0.001), portal inflammation (ß = 0.291; P = 0.030), and absence of an ileocecal valve (ß = 0.267; P = 0.048) were predictive for fibrosis stage.

CONCLUSION

Despite resolution of cholestasis and portal inflammation, significant liver fibrosis and steatosis persist after weaning off PN. Extensive small intestinal resection was the major predictor for liver fibrosis stage.

The gut mucosal immune system in the neonatal period

Invasive sepsis in the newborn period is a major cause of childhood morbidity and mortality worldwide. The infant immune system undoubtedly differs intrinsically from the mature adult immune system. Current understanding is that the newborn infant immune system displays a range of competencies and is developing rather than deficient. The infant gut mucosal immune system is complex and displays a plethora of phenotypic and functional irregularities that may be clinically important. Various factors affect and modulate the infant gut mucosal immune system: components of the intestinal barrier, the infant gut microbiome, nutrition and the maternal-infant hybrid immune system. Elucidation of the phenotypic distribution of immune cells, their functional significance and the mucosa-specific pathways used by these cells is essential to the future of research in the field of infant immunology.

Effect of intestinal atrophy and hepatic impairment induced by parenteral nutrition on drug absorption and disposition in rats

BACKGROUND

Long-term parenteral nutrition (PN) has a high risk of hepatic dysfunction and intestinal atrophy. The present study investigated the effect of PN-induced intestinal atrophy and hepatic impairment on drug pharmacokinetics by using 2 contrasting compounds: phenolsulfonphthalein (PSP) and cyclosporin A (CyA).

MATERIALS AND METHODS

PSP or CyA was administered to 7-day PN-fed Rats (PN rats) and sham operated rats (control rats) via intravenous (IV) or intraloop administration of the intestine. Pharmacokinetic parameters with 2-compartment analysis including area under the concentration vs time curve (AUC) and the permeability after in situ intraloop administration (P loop) were obtained from both concentration profiles after different administration routes.

RESULTS

After IV administration of PSP to control and PN rats, there was no notable difference in any of the pharmacokinetic parameters. In contrast, after intraloop administration, AUC and P loop in PN rats were approximately 2.6- and 2.0-fold higher than that in control rats, respectively. On the other hand, after IV administration of CyA, the terminal half-life and total body clearance were prolonged and decreased in PN rats, respectively, resulting in 2.0-fold increase in AUC. After intraloop administration, the AUC of PN rats was increased to approximately 1.3-fold that of control rats, whereas no notable difference was observed in P loop.

CONCLUSION

The intestinal permeability of PSP was enhanced by intestinal atrophy induced by PN, while the metabolism of CyA was diminished by hepatic impairment by PN. These results revealed the physicochemical property-based pharmacokinetic alterations during PN; for a more detailed understanding, however, further studies are needed.

Effects on varying intravenous lipid emulsions on the small bowel epithelium in a mouse model of parenteral nutrition

BACKGROUND

Injectable fat emulsions (FEs) are a clinically dependable source of essential fatty acids (FA). ω-6 FA is associated with an inflammatory response. Medium-chain triglycerides (MCT, ω-3 FA), fish oil, and olive oil are reported to decrease the inflammatory response. However, the effect of these lipids on the gastrointestinal tract has not been well studied. To address this, we used a mouse model of parenteral nutrition (PN) and hypothesized that a decrease in intestinal inflammation would be seen when either fish oil and MCT or olive oil were added.

METHODS

Three FEs were studied in adult C57BL/6 mice via intravenous cannulation: standard soybean-based FE (SBFE), 80% olive oil -supplemented FE (OOFE), or a combination of a soybean oil, MCT, olive oil, and fish oil emulsion (SMOF). PN was given for 7 days, small bowel mucosa-derived cytokines, animal survival rate, epithelial cell (EC) proliferation and apoptosis rates, intestinal barrier function and mucosal FA composition were analyzed.

RESULTS

Compared to the SBFE and SMOF groups, the best survival, highest EC proliferation and lowest EC apoptosis rates were observed in the OOFE group; and associated with the lowest levels of tumor necrosis factor-α, interleukin-6, and interleukin-1β expression. Jejunal FA content showed higher levels of eicosapentaenoic and docosapentaenoic acid in the SMOF group and the highest arachidonic acid in the OOFE group.

CONCLUSION

The study showed that PN containing OOFE had beneficial effects to small bowel health and animal survival. Further investigation may help to enhance bowel integrity in patients restricted to PN.

Total parenteral nutrition-associated lamina propria inflammation in mice is mediated by a MyD88-dependent mechanism

Enteral nutrient deprivation via total parenteral nutrition (TPN) administration leads to local mucosal inflammatory responses, but the underlying mechanisms are unknown. Wild-type (WT) and MyD88(-/-) mice underwent jugular vein cannulation. One group received TPN without chow, and controls received standard chow. After 7 d, we harvested intestinal mucosally associated bacteria and isolated small-bowel lamina propria (LP) cells. Bacterial populations were analyzed using 454 pyrosequencing. LP cells were analyzed using quantitative PCR and multicolor flow cytometry. WT, control mucosally associated microbiota were Firmicutes-dominant, whereas WT TPN mice were Proteobacteria-domiant. Similar changes were observed in MyD88(-/-) mice with TPN administration. UniFrac analysis showed divergent small bowel and colonic bacterial communities in controls, merging toward similar microbiota (but distinct from controls) with TPN. The percentage of LP T regulatory cells significantly decreased with TPN in WT mice. F4/80(+)CD11b(+)CD11c(dull/-) macrophage-derived proinflammatory cytokines significantly increased with TPN. These proinflammatory immunologic changes were significantly abrogated in MyD88(-/-) TPN mice. Thus, TPN administration is associated with significant expansion of Proteobacteria within the intestinal microbiota and increased proinflammatory LP cytokines. Additionally, MyD88 signaling blockade abrogated decline in epithelial cell proliferation and epithelial barrier function loss.

Intestinal microbial diversity and perioperative complications

BACKGROUND AND AIMS

Enteral nutrient deprivation via parenteral nutrition (PN) in a mouse model leads to a local mucosal inflammatory response. This proinflammatory response leads to a loss of epithelial barrier function and atrophy of the intestine. Although the underlying mechanisms are unknown, a potential contributing factor is the impact PN has on the intestinal microbiome. We recently identified a shift in the intestinal microbial community in mice given PN; however, it is unknown whether such changes occur in humans. We hypothesized that similar microbial changes occur in humans during periods of enteral nutrient deprivation.

METHODS

A series of small bowel specimens were obtained from pediatric and adult patients undergoing small intestinal resection. Mucosally associated bacteria were harvested and analyzed using 454 pyrosequencing techniques. Statistical analysis of microbial diversity and differences in microbial characteristics were assessed between enterally fed and enterally deprived portions of the intestine. Occurrence of postoperative infectious and anastomotic complications was also examined.

RESULTS

Pyrosequencing demonstrated a wide variability in microbial diversity within all groups. Principal coordinate analysis demonstrated only a partial stratification of microbial communities between fed and enterally deprived groups. Interestingly, a tight correlation was identified in patients who had a low level of enteric microbial diversity and those who developed postoperative enteric-derived infections or intestinal anastomotic disruption.

CONCLUSIONS

Loss of enteral nutrients and systemic antibiotic therapy in humans is associated with a significant loss of microbial biodiversity within the small bowel mucosa. These changes were associated with a number of enteric-derived intestinal infections and intestinal anastomotic disruptions.

Colonic enteric nervous system analysis during parenteral nutrition

INTRODUCTION

Parenteral nutrition (PN) is a necessary therapy used to feed patients with gastrointestinal dysfunction. Unfortunately, PN results in intestinal atrophy and changes to host immune function. PN may also induce additional effects on gut motility that we hypothesized would result from changes in the enteric nervous system.

METHODS

Mice received an intravenous (i.v.) catheter and were randomized to chow (n = 5), i.v. PN (n = 6), or i.v. PN + bombesin (BBS, 15 μg/kg, 3×/d) (n = 6) for 5 d. Colons were removed and dissected to measure the length and circumference. Enteric neuronal density and neurotransmitter expression were determined by co-immunostaining whole-mount tissue with Hu and neuronal nitric oxide synthase (nNOS).

RESULTS

The number of myenteric neurons expressing Hu and nNOS increased per unit length in the mid-colon during PN treatment compared with chow. This increase was abrogated by the addition of BBS to the PN regimen. However, the percentage of nNOS-expressing neurons was not significantly altered by PN. Morphometric analysis revealed a decrease in the length and circumference of the colon during PN administration that was partially normalized by supplementation of PN with BBS. A significant reduction in total fecal output was observed in PN animals compared with chow and was increased by mice receiving BBS in addition to PN.

CONCLUSIONS

PN causes a constriction of the bowel wall, reducing not only the length but also the circumference of the colon. These changes cause a condensation of enteric neurons but no difference in neurotransmitter expression. BBS supplementation partially restores the constriction and increases the fecal output during PN treatment compared with PN treatment alone.

Total parenteral nutrition induces a shift in the Firmicutes to Bacteroidetes ratio in association with Paneth cell activation in rats

The use of total parenteral nutrition (TPN) in the treatment of critically ill patients has been the subject of debate because it has been associated with disturbances in intestinal homeostasis. Important factors in maintaining intestinal homeostasis are the intestinal microbiota and Paneth cells, which exist in a mutually amendable relationship. We hypothesized that the disturbed intestinal homeostasis in TPN-fed individuals results from an interplay between a shift in microbiota composition and alterations in Paneth cells. We studied the microbiota composition and expression of Paneth cell antimicrobial proteins in rats receiving TPN or a control diet for 3, 7, or 14 d. qPCR analysis of DNA extracts from small intestinal luminal contents of TPN-fed rats showed a shift in the Firmicutes:Bacteroidetes ratio in favor of Bacteroidetes after 14 d (P < 0.05) compared with the control group. This finding coincided with greater staining intensity for lysozyme and significantly greater mRNA expression of the Paneth cell antimicrobial proteins lysozyme (P < 0.05), rat α-defensin 5 (P < 0.01), and rat α-defensin 8 (P < 0.01). Finally, 14 d of TPN resulted in greater circulating ileal lipid-binding protein concentrations (P < 0.05) and greater leakage of horseradish peroxidase (P < 0.01), which is indicative of enterocyte damage and a breached intestinal barrier. Our findings show a shift in intestinal microbiota in TPN-fed rats that correlated with changes in Paneth cell lysozyme expression (r(s) = -0.75, P < 0.01). Further studies that include interventions with microbiota or nutrients that modulate them may yield information on the involvement of the microbiota and Paneth cells in TPN-associated intestinal compromise.

Influence of defunctionalization and mechanical forces on intestinal epithelial wound healing

The influence on mucosal healing of luminal nutrient flow and the forces it creates are poorly understood. We hypothesized that altered deformation and extracellular pressure mediate, in part, the effects of defunctionalization on mucosal healing. We created patent or partially obstructing defunctionalizing jejunal Roux-en-Y anastomoses in rats to investigate mucosal healing in the absence or presence of luminal nutrient flow and measured luminal pressures to document partial obstruction. We used serosal acetic acid to induce ulcers in the proximal, distal, and defunctionalized intestinal segments. After 3 days, we assessed ulcer area, proliferation, and phosphorylated ERK. In vitro, we measured proliferation and migration in Caco-2 and IEC-6 intestinal epithelial cells subjected to cyclic strain, increased extracellular pressure, or strain and pressure together. Defunctionalization of intestine without obstruction reduced phosphorylated ERK, slowed ulcer healing, and inhibited mucosal proliferation. This outcome was blocked by PD-98059. Partial obstruction delayed ulcer healing but stimulated proliferation independently of ERK. In vitro, strain increased Caco-2 and IEC-6 proliferation and reduced migration across collagen but reduced proliferation and increased migration across fibronectin. In contrast, increased pressure and the combination of pressure and strain increased proliferation and reduced migration independently of substrate. PD-98059 reduced basal migration but increased migration under pressure. These results suggest that loss of the repetitive distension may decrease mucosal healing in defunctionalized bowel, while increased luminal pressure above anastomoses or in spastic bowel disease could further inhibit mucosal healing, despite peristaltic repetitive strain. ERK may mediate the effects of repetitive deformation but not the effects of pressure.

Loss of enteral nutrition in a mouse model results in intestinal epithelial barrier dysfunction

Total parenteral nutrition (TPN) administration in a mouse model leads to a local mucosal inflammatory response, resulting in a loss of epithelial barrier function (EBF). Although, the underlying mechanisms are unknown, a major contributing factor is a loss of growth factors and subsequent critical downstream signaling. An important component of these is the p-Akt pathway. An additional contributing factor to the loss of EBF with TPN is an increase in proinflammatory cytokine abundance within the mucosal epithelium, including TNF-α and IFN-γ. Loss of critical nutrients, including glutamine and glutamate, may affect EBF, contributing to the loss of tight junction proteins. Finding protective modalities for the small intestine during TPN administration may have important clinical applications. Supplemental glutamine and glutamate may be examples of such agents.

Toll-like receptor 4-dependent Kupffer cell activation and liver injury in a novel mouse model of parenteral nutrition and intestinal injury

Infants with intestinal failure who are parenteral nutrition (PN)-dependent may develop cholestatic liver injury and cirrhosis (PN-associated liver injury: PNALI). The pathogenesis of PNALI remains incompletely understood. We hypothesized that intestinal injury with increased intestinal permeability combined with administration of PN promotes lipopolysaccharide (LPS)-Toll-like receptor 4 (TLR4) signaling dependent Kupffer cell (KC) activation as an early event in the pathogenesis of PNALI. We developed a mouse model in which intestinal injury and increased permeability were induced by oral treatment for 4 days with dextran sulphate sodium (DSS) followed by continuous infusion of soy lipid-based PN solution through a central venous catheter for 7 (PN7d/DSS) and 28 (PN28d/DSS) days. Purified KCs were probed for transcription of proinflammatory cytokines. PN7d/DSS mice showed increased intestinal permeability and elevated portal vein LPS levels, evidence of hepatocyte injury and cholestasis (serum aspartate aminotransferase, alanine aminotransferase, bile acids, total bilirubin), and increased KC expression of interleukin-6 (Il6), tumor necrosis factor α (Tnfα), and transforming growth factor β (Tgfβ). Markers of liver injury remained elevated in PN28d/DSS mice associated with lobular inflammation, hepatocyte apoptosis, peliosis, and KC hypertrophy and hyperplasia. PN infusion without DSS pretreatment or DSS pretreatment alone did not result in liver injury or KC activation, even though portal vein LPS levels were elevated. Suppression of the intestinal microbiota with broad spectrum antibiotics or ablation of TLR4 signaling in Tlr4 mutant mice resulted in significantly reduced KC activation and markedly attenuated liver injury in PN7d/DSS mice.

CONCLUSION

These data suggest that intestinal-derived LPS activates KC through TLR4 signaling in early stages of PNALI.

Changes in morphology and function in small intestinal mucosa after Roux-en-Y surgery in a rat model

BACKGROUND

Currently there is no an appropriate model to study intestinal mucosal atrophy in vivo that preserves the nutritional status of the organism.

MATERIALS AND METHODS

We created a defunctionalized segment of jejunum via a dead-end Roux-en-Y anastomosis in rats. We compared tissue morphometric parameters in the intestinal mucosa of the defunctionalized bowel with that of the mucosa proximal and distal to the anastomosis. We further measured extracellular signal-regulated kinase (ERK) activation within the mucosa as well as sucrase-isomaltase and dipeptidyl peptidase-4 levels as markers of intestinal mucosal differentiation by Western blotting of mucosal scrapings.

RESULTS

Three days after anastomosis, the defunctionalized bowel exhibited decreased diameter and thickness of both the mucosa and the fibromuscular layer compared with adjacent bowel in continuity for luminal nutrient flow or with bowel from control animals. Sucrase-isomaltase and dipeptidyl peptidase-4 levels also were decreased. Furthermore, mucosal ERK activation, assessed as the ratio of phosphorylated to total ERK, also was reduced. Animal weights did not differ between bypassed and control animals.

CONCLUSIONS

Deprivation of nutrient flow in a segment of bowel by defunctionalizing Roux-en-anastomosis produces mucosal atrophy as indicated by altered histology, differentiation marker expression, and ERK signaling, in animals that are otherwise able to maintain enteral nutrition.

Distraction-induced intestinal enterogenesis: preservation of intestinal function and lengthening after reimplantation into normal jejunum

BACKGROUND

Significant bowel lengthening can occur in an isolated intestinal segment with the use of linearly directed distractive forces, resulting in increased surface area and epithelial cell proliferation. We hypothesized that reimplantation of this lengthened intestine into normal jejunum would preserve this gain in intestinal length and function similar to normal jejunum.

METHODS

An intestinal lengthening device was inserted into isolated jejunal segments in pigs, and fully expanded over 8 days. Lengthened segments were then reimplanted into normal intestinal continuity. Pigs were studied after another 28 days. Function was assessed by motility, mucosal enzyme activity, barrier function, and intestinal ion transport.

RESULTS

Lengthened segments were significantly longer than control segments and had nearly 2-fold greater surface area. Bowel lengthening was maintained 4 weeks after reimplantation. Motility after reimplantation was similar to nonoperated pigs. Barrier function, mucosal disaccharidase levels, and electrophysiologic measures declined immediately after lengthening but returned to nearly normal levels 28 days after reimplantation.

CONCLUSION

Bowel lengthening results in a transient decline in mucosal absorptive function and smooth muscle contractility. However, function approaches that of normal bowel after reimplantation into enteric flow. These data may support the use of this technique as a potential new option for the treatment of patients with short bowel syndrome.

Cellular uptake and cytotoxicity of chitosan-caseinophosphopeptides nanocomplexes loaded with epigallocatechin gallate

Epigallocatechin gallate (EGCG) was successfully encapsulated in novel nanocomplexes assembled from bioactive peptides, caseinophosphopeptides (CPPs), and chitosan (CS), a natural cationic polymer. Their particle sizes and surface charges were determined to be in the range of 150.0±4.3 nm and 32.2±3.3 mV respectively. Crosslinking between the -NH3+ groups of CS with the -P=O- and -COO- groups of CPP, as well as the hydrogen bonding were confirmed from the FTIR results. Atomic force microscopy (AFM) images showed that EGCG loaded CS-CPP nanocomplexes were spherical in shape. Maintaining the surface charge as high as +32.2 mV, crosslinking CS with peptides reduced the cytotoxicity of CS nanoparticles. In addition, cellular internalization of EGCG-loaded CS-CPP nanoparticles was confirmed from green fluorescence inside the Caco-2 cells. The process of nanoparticle uptake was dose and time dependent in the range of time and concentration studied. Furthermore, the intestinal permeability of EGCG using Caco-2 monolayer was enhanced significantly as delivered by nanoparticles, which indicated the promising elevation of EGCG bioavailability.

Chitosan nanoparticles enhance the plasma exposure of (-)-epigallocatechin gallate in mice through an enhancement in intestinal stability

The green tea catechin (-)-epigallocatechin gallate (EGCG) has attracted significant research interest due to its beneficial therapeutic effects, which include anti-oxidant, neuro-protective and anti-cancer effects. However, the therapeutic potential of EGCG following oral consumption is limited by its poor absorption. To address this issue, EGCG has been encapsulated in chitosan-tripolyphosphate nanoparticles (CS NPs) and the oral absorption of EGCG evaluated in Swiss Outbred mice. Administration of the CS NPs enhanced the plasma exposure of total EGCG by a factor of 1.5 relative to an EGCG solution, with plasma AUC((0-5 h)) values of 116.4±4.1 and 179.3±10.8 nM.h (mean±s.d., n=3-5) for the EGCG solution and CS NPs, respectively. Associated with the increased plasma exposure of EGCG was an enhancement in concentrations of EGCG in the stomach and jejunum of mice following CS NP administration. A 2.3-fold increase in the apparent exposure of EGCG to the jejunum (AUC(j)) was observed following CS NP encapsulation, with AUC(j(0-5 h)) values of 5.3±1.1 and 12.3±1.5 μM.h (mean±s.d., n=3-5) for the EGCG solution and CS NPs, respectively. The enhanced exposure of EGCG to the jejunum was likely responsible for the increased plasma concentrations of EGCG. The findings from this study suggest that CS NPs may be a useful approach for enhancing oral delivery, and therapeutic application, of EGCG in a number of disease conditions.

Use of enterally delivered angiotensin II type Ia receptor antagonists to reduce the severity of colitis

BACKGROUND

Renin-angiotensin system blockade reduces inflammation in several organ systems. Having found a fourfold increase in angiotensin II type Ia receptor expression in a dextran sodium sulfate colitis model, we targeted blockade with angiotensin II type Ia receptor antagonists to prevent colitis development. Because hypotension is a major complication of angiotensin II type Ia receptor antagonists use, we hypothesized that use of angiotensin II type Ia receptor antagonists compounds which lack cell membrane permeability, and thus enteric absorption, would allow for direct enteral delivery at far higher concentrations than would be tolerated systemically, yet retain efficacy.

METHODS

Based on the structure of the angiotensin II type Ia receptor antagonist losartan, deschloro-losartan was synthesized, which has extremely poor cell membrane permeability. Angiotensin II type Ia receptor antagonist efficacy was evaluated by determining the ability to block NF-κB activation in vitro. Dextran sodium sulfate colitis was induced in mice and angiotensin II type Ia receptor antagonist efficacy delivered transanally was assessed.

RESULTS

In vitro, deschloro-losartan demonstrated near equal angiotensin II type Ia receptor blockade compared to losartan as well as another angiotensin II type Ia receptor antagonist, candesartan. In the dextran sodium sulfate model, each compound significantly improved clinical and histologic scores and epithelial cell apoptosis. Abundance of TNF-α, IL-1β, and IL6 mRNA were significantly decreased with each compound. In vitro and in vivo intestinal drug absorption, as well as measures of blood pressure and mucosal and colonic blood flow, showed significantly lower uptake of deschloro-losartan compared to losartan and candesartan.

CONCLUSIONS

This study demonstrated efficacy of high-dose angiotensin II type Ia receptor antagonists in this colitis model. We postulate that a specially designed angiotensin II type Ia receptor antagonist with poor oral absorption may have great potential as a new therapeutic agent for inflammatory bowel disease in the future.

Chitosan nanoparticles enhance the intestinal absorption of the green tea catechins (+)-catechin and (-)-epigallocatechin gallate

Catechins found in green tea have received considerable attention due to their favourable biological properties which include cardioprotective, neuroprotective and anti-cancer effects. However, their therapeutic potential is limited by their low oral bioavailability, attributed to poor stability and intestinal absorption. We encapsulated (+)-catechin (C) and (-)-epigallocatechin gallate (EGCg) in chitosan nanoparticles (CS NP) as a means of enhancing their intestinal absorption. Using excised mouse jejunum in Ussing chambers, encapsulation significantly enhanced (p<0.05) intestinal absorption. The cumulative amounts transported after encapsulation were significantly higher (p<0.05), i.e. 302.1+/-46.1 vs 206.8+/-12.6ng/cm(2) and 102.7+/-12.4 vs 57.9+/-7.9ng/cm(2) for C and EGCg, respectively. The mechanism by which absorption was enhanced was not through an effect of CS NPs on intestinal paracellular or passive transcellular transport processes (as shown by transport of (14)C-mannitol and (3)H-propranolol) or an effect on efflux proteins (as shown by transport of (3)H-digoxin) but was likely due to stabilization of catechins after encapsulation (99.7+/-0.7 vs 94.9+/-3.8% and 56.9+/-3.0 vs 1.3+/-1.7% of the initial C and EGCg concentration remaining, respectively). This study demonstrates that encapsulation of catechins in CS NPs enhances their intestinal absorption and is a promising strategy for improving their bioavailability.

Fasting-induced intestinal apoptosis is mediated by inducible nitric oxide synthase and interferon-{gamma} in rat

Nitric oxide (NO) is associated with intestinal apoptosis in health and disease. This study aimed to investigate the role of intestinal NO in the regulation of apoptosis during fasting in rats. Male Wistar rats were divided into two groups and subcutaneously injected with saline (SA) or aminoguanidine (AG), followed by fasting for 24, 48, 60, and 72 h. At each time point, the jejunum was subjected to histological evaluation for enterocyte apoptosis by histomorphometric assessment and TUNEL analysis. We performed immunohistochemistry for inducible NO synthase (iNOS) expression in the jejunum and measured tissue nitrite levels using HPLC and 8-hydroxydeoxyguanosine adduct using ELISA, indicative of endogenous NO production and reactive oxygen species (ROS) production, respectively. Jejunal transcriptional levels of iNOS, neuronal NO synthase (nNOS), and interferon-gamma (IFN-gamma) were also determined by RT-PCR. Fasting caused significant jejunal mucosal atrophy due to attenuated cell proliferation and enhanced apoptosis with increase in iNOS transcription, its protein expression in intestinal epithelial cells (IEC), and jejunal nitrite levels. However, AG treatment histologically reduced apoptosis with inhibition of fasting-induced iNOS transcription, protein expression, and nitrite production. We also observed fasting-induced ROS production and subsequent IFN-gamma transcription, which were all inhibited by AG treatment. Furthermore, we observed reduced transcriptional levels of nNOS, known to suppress iNOS activation physiologically. These results suggest that fasting-induced iNOS activation in IEC may induce apoptosis mediators such as IFN-gamma via a ROS-mediated mechanism and also a possible role of nNOS in the regulation of iNOS activity in fasting-induced apoptosis.

Glutamine prevents total parenteral nutrition-associated changes to intraepithelial lymphocyte phenotype and function: a potential mechanism for the preservation of epithelial barrier function

Total parenteral nutrition (TPN) results in a number of derangements to the intestinal epithelium, including a loss of epithelial barrier function (EBF). As TPN supplemented with glutamine has been thought to prevent this loss, this article further defined the impact of glutamine on EBF, and investigated potential mechanisms that contributed to the preservation of EBF. C57BL/6J male mice were randomized to enteral nutrition (control), TPN, or TPN supplemented with glutamine (TPN+GLN). Changes in intraepithelial lymphocyte (IEL)-derived cytokine expression were measured, and EBF was assessed with electrophysiologic methods and assessment of junctional protein expression. TPN resulted in a significant decline in EBF, and this loss of EBF was significantly prevented in the TPN+GLN group. Coincident with these changes was a loss of intraepithelial lymphocyte (IEL, mucosal lymphocyte)-derived IL-10 and increase in interferon-gamma (IFN-gamma) expression, and a decline in IEL numbers in the TPN group. A prevention in the increase in IFN-gamma and decline in IL-10 expression was seen in the TPN+GLN group. To determine the mechanism responsible for these glutamine-associated cytokine changes, we tested whether blockade of the IL-7 signaling pathway between epithelial cells (EC) and IEL would prevent these changes; however, blockade failed to influence IEL-derived cytokine changes. Glutamine-supplemented TPN leads to a specific IEL-derived cytokine profile, which may account for the preservation of EBF; and such action may be due to a direct action of glutamine on the IEL.

Enteral versus parenteral nutrition: effect on intestinal barrier function

Total parenteral nutrition (TPN), or the complete absence of enteral nutrients, is commonly used in a clinical setting. However, a major consequence of TPN administration is the development of mucosal atrophy and a loss of epithelial barrier function (EBF); and this loss may lead to an increase in clinical infections and septicemia. Our laboratory has investigated the mechanism of this TPN-associated loss of EBF using a mouse model. We have demonstrated that the mucosal lymphoid population significantly changes with TPN, and leads to a rise in interferon gamma (IFN-gamma) and decline in interleukin-10 (IL-10) expression-both of which contribute to the loss of EBF. Associated with these cytokine changes is a dramatic decline in the expression of tight junction and adherens junction proteins. This article discusses the potential mechanisms responsible for these changes, and potential strategies to alleviate this loss in EBF.

Up-regulation of intestinal Toll-Like receptors and cytokines expressions change after TPN administration and a lack of enteral feeding

BACKGROUND

Total parenteral nutrition (TPN) increases the risk of severe infectious complications such as septic shock, which are believed to be the result of a breakdown of intestinal barrier function and subsequent bacterial translocation. Toll-like receptors (TLRs) comprise a family of membrane proteins that serve as pattern recognition receptors for a variety of microbe-derived molecules and stimulate innate immune responses to microbes. Alteration of intraepithelial lymphocytes (IELs) to TPN administration has been studied extensively. However, few studies have examined the effect of TPN administration on intestinal TLRs. We hypothesized that the expressions of intestinal TLRs and cytokines may change with TPN administration and a lack of enteral feeding.

MATERIALS AND METHODS

TPN-treated mice and sham operation mice (control) were killed at 10 days after operation. mRNA expression of intestinal cytokines and TLRs were analyzed with reverse transcription-polymerase chain reaction (RT-PCR) methods. Change in IEL populations was analyzed with flow cytometry.

RESULTS

RT-PCR showed varying expression levels of TLRs at different sites on the small intestine and colon. TLR4, TLR5, TLR7, and TLR9 mRNAs were up-regulated in response to TPN administration, particularly in the distal small intestine.

CONCLUSIONS

Up-regulation of TLRs in intestine in response to TPN administration and a lack of enteral nutrition may be associated with an increased risk of septic shock due to bacterial translocation caused by Interferon gamma-mediated intestinal epithelial cell apoptosis.

Alteration of canalicular transporters in a mouse model of total parenteral nutrition

OBJECTIVES

Parenteral nutrition-associated liver disease (PNALD) is a major problem with prolonged total parenteral nutrition (TPN) administration. Our laboratory previously demonstrated significant changes in the expression of multidrug resistance genes (MDRs) 1 and 2, hepatocyte transporters, in a TPN mouse model. The present study hypothesized that these changes would lead to functional changes in the liver, and would contribute to the development of liver dysfunction.

MATERIALS AND METHODS

Mice received either intravenous saline and standard chow or TPN with or without intravenous lipids. Functional assays were performed after 7 days of infusion.

RESULTS

TPN with lipids led to a significant increase in serum bile acid levels, consistent with an early state of PNALD. Use of TPN without lipids prevented an elevation in bile acid levels. In both TPN groups, MDR2 expression was significantly (68%) lower than controls and bile phosphatidylcholine content, a functional measure of MDR2, was 40% less than controls. MDR1 expression in the TPN with lipid group was 31% higher than controls, whereas in the TPN without lipids mice there was no significant change. Hepatocyte extrusion of rhodamine dye, a measure of MDR1 function, declined only in the TPN with lipid group. Peroxisome proliferator-activated receptor-alpha expression decreased in both TPN groups. Fenofibrate given with TPN resulted in an increased expression of MDR1 and MDR2, and functionally increased hepatocyte rhodamine extrusion and presence of bile phosphatidylcholine in the TPN with lipid group.

CONCLUSIONS

The study shows that TPN led to alterations in the function of MDR1- and MDR2-expressed proteins. The changes help in the understanding of the mechanisms leading to PNALD, and suggest that fibrate administration may palliate these changes.

Dissociation of E-cadherin and beta-catenin in a mouse model of total parenteral nutrition: a mechanism for the loss of epithelial cell proliferation and villus atrophy

Total parenteral nutrition (TPN) leads a loss of epithelial barrier function, decline in epithelial cell (EC) proliferation, and decreased expression of E-cadherin. As a large portion of intracellular beta-catenin is tightly associated with E-cadherin, we hypothesized that the loss of E-cadherin would result in a redistribution of intracellular beta-catenin, and could be a contributing mechanism for this TPN-associated loss of EC proliferation. An assessment of small bowel epithelium was performed in mice given either enteral nutrition (Control) or intravenous nutrition (TPN). TPN significantly down-regulated E-cadherin and beta-catenin expression, and resulted in a loss of a colocalization of these factors. TPN also up-regulated phosphorylated (p)-beta-catenin (Ser31/33,Thr41) and down-regulated (p)-beta-catenin(Ser552) expression. To further address mechanisms driving this, we observed a significant decrease in the abundance of p-AKT and p-GSK3beta expression, and an associated decline in tcf-4 transcription factors (cyclin D1, c-myc and Axin2), as well as a loss of EC proliferation by 7 days. To address whether the mechanism driving these changes was the absence of nutritional factors, glutamine was added to the TPN solution. This resulted in a partial restoration of beta-catenin expression and EC proliferation, suggesting that an alteration in nutrient delivery may affect many of these changes. Based on these findings, the loss of EC proliferation with TPN may well be due to a loss of total beta-catenin, as well as a concomitant change in the differential expression of beta-catenin phosphorylation sites, and a reduction in beta-catenin mediated tcf-4 transcription. This potential pathway may well explain many of the findings of mucosal atrophy associated with TPN.