The gut's role in metabolism, mucosal barrier function, and gut immunology

Three-Dimensional Scaffolds for Intestinal Cell Culture: Fabrication, Utilization, and Prospects

The intestine is a visceral organ that integrates absorption, metabolism, and immunity, which is vulnerable to external stimulus. Researchers in the fields such as food science, immunology, and pharmacology have committed to developing appropriate in vitro intestinal cell models to study the intestinal absorption and metabolism mechanisms of various nutrients and drugs, or pathogenesis of intestinal diseases. In the past three decades, the intestinal cell models have undergone a significant transformation from conventional two-dimensional cultures to three-dimensional (3D) systems, and the achievements of 3D cell culture have been greatly contributed by the fabrication of different scaffolds. In this review, we first introduce the developing trend of existing intestinal models. Then, four types of scaffolds, including Transwell, hydrogel, tubular scaffolds, and intestine-on-a-chip, are discussed for their 3D structure, composition, advantages, and limitations in the establishment of intestinal cell models. Excitingly, some of the in vitro intestinal cell models based on these scaffolds could successfully mimic the 3D structure, microenvironment, mechanical peristalsis, fluid system, signaling gradients, or other important aspects of the original human intestine. Furthermore, we discuss the potential applications of the intestinal cell models in drug screening, disease modeling, and even regenerative repair of intestinal tissues. This review presents an overview of state-of-the-art scaffold-based cell models within the context of intestines, and highlights their major advances and applications contributing to a better knowledge of intestinal diseases. Impact statement The intestine tract is crucial in the absorption and metabolism of nutrients and drugs, as well as immune responses against external pathogens or antigens in a complex microenvironment. The appropriate experimental cell model in vitro is needed for in-depth studies of intestines, due to the limitation of animal models in dynamic control and real-time assessment of key intestinal physiological and pathological processes, as well as the "R" principles in laboratory animal experiments. Three-dimensional (3D) scaffold-based cell cultivation has become a developing tendency because of the superior cell proliferation and differentiation and more physiologically relevant environment supported by the customized 3D scaffolds. In this review, we summarize four types of up-to-date 3D cell culture scaffolds fabricated by various materials and techniques for a better recapitulation of some essential physiological and functional characteristics of original intestines compared to conventional cell models. These emerging 3D intestinal models have shown promising results in not only evaluating the pharmacokinetic characteristics, security, and effectiveness of drugs, but also studying the pathological mechanisms of intestinal diseases at cellular and molecular levels. Importantly, the weakness of the representative 3D models for intestines is also discussed.

Alteration in the Population of Intraepithelial Lymphocytes and Virus Shedding in Specific-Pathogen-Free Chickens Following Inoculation with Lentogenic and Velogenic Newcastle Disease Virus Strains

Intraepithelial lymphocytes (IELs) provide the first line of immunological defense after the invasion of the intestine by a pathogen. To understand the changes of IEL response in chickens, we measured the population of different subsets of avian IELs at different time points after primary inoculation of Newcastle disease virus (NDV) lentogenic strain (LaSota) and subsequent challenge with NDV velogenic strain- genotypes VII and VIII. Furthermore, NDV shed after each treatment was quantified. Specific-pathogen-free chickens were randomly divided into six groups of chickens, one to six, inoculated with phosphate buffered saline; NDV lentogenic strain (LaSota); genotype VII (GVII); LaSota and challenged with GVII (LSGVII); genotype VIII (GVIII); and group of LaSota and challenged with GVIII (LSGVIII). The chickens were euthanized at 12, 36, and 60 h postchallenge. Immunophenotyping of CD25⁺ IEL, CD3⁺ cells, CD4⁺ cells, and CD8⁺ cells was conducted using flow cytometer. Furthermore, virus shedding was measured using reverse transcriptase-quantitative polymerase chain reaction. Data were analyzed using a two-way analysis of variance (ANOVA). The results showed that the percentage population of IEL subsets was generally lower in the chickens inoculated with GVII or GVIII when compared with LaSota, LSGVII and LSGVIII inoculated groups. The NDV copy number was significantly higher in chickens challenged with NDV GVII or GVIII when compared with chickens inoculated with LaSota, LSGVII or LSGVIII. Taking together, NDV velogenic strain caused decrease in the population of subsets of chickens' IEL. However, inoculation of NDV LaSota may increase the population of avian IEL subsets and decrease shedding of virulent NDV.

Betulinic acid attenuates cyclophosphamide-induced intestinal mucosa injury by inhibiting the NF-κB/MAPK signalling pathways and activating the Nrf2 signalling pathway

Betulinic acid (BA), a pentacyclic triterpenoid, has been associated with several biological effects, such as antioxidant, anti-inflammatory and antiviral activities. Previous studies have demonstrated that BA has the ability to alleviate intestinal mucosal damage, however, the potential mechanism associated with the effect has not been reported. This study aimed to investigate the possible protective mechanism of BA against cyclophosphamide (CYP)-induced intestinal mucosal damage. Here, we found that BA pretreatment prevented intestinal mucosal barrier dysfuction from CYP-challenged mice by repairing the intestinal physical, chemical, and immune barriers. Moreover, BA treatment suppressed the CYP-induced oxidative stress by activating the nuclear factor erythroid 2 [NF-E2]-related factor (Nrf2) pathway blocked reactive oxygen species (ROS) accumulation. In addition, BA inhibited CYP-triggered intestinal inflammation through down-regulating the nuclear transcription factor kappa B (NF-κB)/mitogen-activating protein kinase (MAPK) pathways. Furthermore, BA pretreatment reduced intestinal apoptosis by blocking ROS-activated mitochondrial apoptotic pathway. Overall, the current study demonstrated the protective effect of BA against CYP-caused intestinal mucosal damage by regulating the Nrf2 and NF-κB/MAPK signalling pathways, which may provide new therapeutic targets to attenuate intestinal impairment and maintain intestinal health.

Ganglioside Alters Phospholipase Trafficking, Inhibits NF-κB Assembly, and Protects Tight Junction Integrity

Background and Aims: Dietary gangliosides are present in human milk and consumed in low amounts from organ meats. Clinical and animal studies indicate that dietary gangliosides attenuate signaling processes that are a hallmark of inflammatory bowel disease (IBD). Gangliosides decrease pro-inflammatory markers, improve intestinal permeability, and reduce symptoms characteristic in patients with IBD. The objective of this study was to examine mechanisms by which dietary gangliosides exert beneficial effects on intestinal health. Methods: Studies were conducted in vitro using CaCo-2 intestinal epithelial cells. Gangliosides were extracted from milk powder and incubated with differentiated CaCo-2 cells after exposure to pro-inflammatory stimuli. Gut barrier integrity was assessed by electron microscopy, epithelial barrier function was examined by measuring transepithelial electric resistance, and content of HBD-2, IL-23, NF-κB, and sPLA₂ was assessed by ELISA. Results: Ganglioside attenuated the decrease in integrity of tight junctions induced by pro-inflammatory stimuli and improved epithelial barrier function (P < 0.05). Ganglioside decreased the basolateral secretion of sPLA₂ (P ≤ 0.05), lowered HBD-2 and IL-23 levels (P ≤ 0.05), and inhibited NF-κB activation (P ≤ 0.05). Conclusions: In summary, the present study indicates that ganglioside GD3 improves intestinal integrity by altering sPLA₂ trafficking, and the production of pro-inflammatory mediators is mitigated by decreasing assembly of the NF-κB complex. Dietary gangliosides may have promising potential beneficial effects in IBD as decreased inflammatory signaling, improved intestinal integrity, and maintenance of epithelial barrier function have been demonstrated in vitro.

Early Initiation of Feeding and In-Hospital Outcomes in Patients Hospitalized for Acute Heart Failure

Extensive data on early nutrition support for patients requiring critical care are available. However, whether early initiation of feeding could be beneficial for patients hospitalized for acute heart failure (HF) remains unclear. We sought to compare outcomes of early and delayed initiation of feeding for hospitalized patients with acute HF using a nationwide inpatient database. We retrospectively analyzed data from the Diagnosis Procedure Combination database. We included patients hospitalized for HF between January 2010 and March 2018. We excluded patients with length of hospital stay ≤2 days, those patients who underwent major procedures under general anesthesia, and those requiring advanced mechanical supports within 2 days after admission including intubation, intra-aortic balloon pumping, and extracorporeal membrane oxygenation. Propensity score matching and instrumental variable analyses were conducted to compare in-hospital mortality, complications and length of stay between the early and delayed feeding groups. Among 432,620 eligible patients, 403,442 patients (93%) received early initiation of feeding (within 2 days after admission) and 29,178 patients (7%) received delayed initiation of feeding. Propensity score matching created 29,153 pairs and delayed initiation of feeding was associated with higher in-hospital mortality (odds ratio 1.32; 95% confidence interval 1.26 to 1.39), longer hospital stay and higher incidence of pneumonia and sepsis. The instrumental variable analysis also showed patients with delayed initiation of feeding had higher in-hospital mortality (odds ratio 1.34; 95% confidence interval 1.28 to 1.40). In conclusion, our analysis suggested a potential benefit of early initiation of feeding for in-hospital outcomes in hospitalized patients hospitalized for acute HF. Further investigations are required to confirm our results and to clarify the underlying mechanisms.

ACVIM consensus statement on pancreatitis in cats

Background

Pancreatitis in cats, although commonly diagnosed, still presents many diagnostic and management challenges.

Objective

To summarize the current literature as it relates to etiology, pathogenesis, diagnosis, and management of pancreatitis in cats and to arrive at clinically relevant suggestions for veterinary clinicians that are based on evidence, and where such evidence is lacking, based on consensus of experts in the field.

Animals

None.

Methods

A panel of 8 experts in the field (5 internists, 1 radiologist, 1 clinical pathologist, and 1 anatomic pathologist), with support from a librarian, was formed to assess and summarize evidence in the peer reviewed literature and complement it with consensus clinical recommendations.

Results

There was little literature on the etiology and pathogenesis of spontaneous pancreatitis in cats, but there was much in the literature about the disease in humans, along with some experimental evidence in cats and nonfeline species. Most evidence was in the area of diagnosis of pancreatitis in cats, which was summarized carefully. In contrast, there was little evidence on the management of pancreatitis in cats.

Conclusions and Clinical Importance

Pancreatitis is amenable to antemortem diagnosis by integrating all clinical and diagnostic information available, and recognizing that acute pancreatitis is far easier to diagnose than chronic pancreatitis. Although both forms of pancreatitis can be managed successfully in many cats, management measures are far less clearly defined for chronic pancreatitis.

Feline comorbidities: What do we really know about feline triaditis?

PRACTICAL RELEVANCE

Feline triaditis describes concurrent pancreatitis, cholangitis and inflammatory bowel disease (IBD). The reported prevalence is 17-39% in ill referral patients. While the aetiology is poorly understood, it is known to include infectious, autoimmune and physical components. What is not known is whether different organs are affected by different diseases, or the same process; indeed, triaditis may be part of a multiorgan inflammatory disease. Feline gastrointestinal tract anatomy plays its role too. Specifically, the short small intestine, high bacterial load and anatomic feature whereby the pancreatic duct joins the common bile duct before entering the duodenal papilla all increase the risk of bacterial reflux and parenchymal inflammation. Inflammation may also be a sequela of bowel bacterial translocation and systemic bacteraemia.

DIAGNOSTIC CHALLENGES

Cholangitis, pancreatitis and IBD manifest with overlapping, vague and non-specific clinical signs. Cholangitis may be accompanied by increased serum liver enzymes, total bilirubin and bile acid concentrations, and variable ultrasonographic changes. A presumptive diagnosis of pancreatitis is based on increased serum pancreatic lipase immunoreactivity or feline pancreas-specific lipase, and/or abnormal pancreatic changes on ultrasonography, though these tests have low sensitivity. Diagnosis of IBD is challenging without histopathology; ultrasound findings vary from normal to mucosal thickening or loss of layering. Triaditis may cause decreased serum folate or cobalamin (B12) concentrations due to intestinal disease and/or pancreatitis. Triaditis can only be confirmed with histopathology; hence, it remains a presumptive diagnosis in most cases.

EVIDENCE BASE

The literature on feline triaditis, pancreatitis, cholangitis and IBD is reviewed, focusing on histopathology, clinical significance and diagnostic challenges. Current management recommendations are provided. Further studies are needed to understand the complex pathophysiology, and in turn improve diagnosis and treatment.

Early enteral nutrition in patients with severe traumatic brain injury: a propensity score-matched analysis using a nationwide inpatient database in Japan

BACKGROUND

Whether enteral nutrition (EN) should be administered early in severe traumatic brain injury (TBI) patients has not been fully addressed.

OBJECTIVE

The present study aimed to evaluate whether early EN can reduce mortality or nosocomial pneumonia among severe TBI patients.

METHODS

Using the Japanese Diagnosis Procedure Combination inpatient database from April 2014 to March 2017 linked with the Survey for Medical Institutions, we identified patients admitted for intracranial injury with Japan Coma Scale scores ≥30 (corresponding to Glasgow Coma Scale scores ≤8) at admission. We designated patients who started EN within 2 d of admission as the early EN group, and those who started EN at 3-5 d after admission as the delayed EN group. The primary outcome was in-hospital mortality. The secondary outcome was nosocomial pneumonia. Propensity score-matched analyses were performed to compare the outcomes between the 2 groups.

RESULTS

We identified 3080 eligible patients during the 36-mo study period, comprising 1100 (36%) in the early EN group and 1980 (64%) in the delayed EN group. After propensity score matching, there was no significant difference in in-hospital mortality (difference: -0.3%; 95% CI: -3.7%, 3.1%) between the 2 groups. The proportion of nosocomial pneumonia was significantly lower in the early EN group than in the delayed EN group (difference: -3.2%; 95% CI: -5.9%, -0.4%).

CONCLUSIONS

Early EN may not reduce mortality, but may reduce nosocomial pneumonia in patients with severe TBI.

Advances and Current Challenges in Intestinal in vitro Model Engineering: A Digest

The physiological environment of the intestine is characterized by its variegated composition, numerous functions and unique dynamic conditions, making it challenging to recreate the organ in vitro. This review outlines the requirements for engineering physiologically relevant intestinal in vitro models, mainly focusing on the importance of the mechano-structural cues that are often neglected in classic cell culture systems. More precisely: the topography, motility and flow present in the intestinal epithelium. After defining quantitative descriptors for these features, we describe the current state of the art, citing relevant approaches used to address one (or more) of the elements in question, pursuing a progressive conceptual construction of an "ideal" biomimetic intestinal model. The review concludes with a critical assessment of the currently available methods to summarize the important features of the intestinal tissue in the light of their different applications.

Enteral Access in Mechanically Ventilated Patients

The early institution of enteral nutrition is now accepted as the preferred route of feeding in critically ill patients with a functioning gastrointestinal tract. It is particularly important to establish early enteral nutrition in mechanically ventilated patients because of the metabolic demands associated with mechanical ventilation. The options for enteral access in mechanically ventilated patients are reviewed, with an emphasis on those techniques that may be performed at the bedside. The advantages, disadvantages, and complications of the different techniques will be considered.

Immunity decreases, antioxidant system damages and tight junction changes in the intestine of grass carp (Ctenopharyngodon idella) during folic acid deficiency: Regulation of NF-κB, Nrf2 and MLCK mRNA levels

This investigation used the same growth trial as the previous study, which showed that folic acid deficiency retarded growth in young grass carp (the percent weight gain of Groups 1-6 were 102.32 ± 3.41%, 137.25 ± 10.48%, 179.78 ± 3.95%, 164.33 ± 3.21%, 143.35 ± 8.12% and 115.28 ± 2.66%) [1]. In the present study, we investigated the effects of dietary folic acid on the immune response, antioxidant status and tight junctions in the intestine of young grass carp (Ctenopharyngodon idella). A total of 540 young grass carp were fed diets containing graded levels of folic acid at 0.10, 0.47, 1.03, 1.48, 1.88 and 3.12 mg kg(-1) diet for 8 weeks. The results indicated that acid phosphatase and lysozyme activities, and the complement component 3 content in the proximal intestine (PI), mid intestine (MI) and distal intestine (DI) were decreased with folic acid deficiency (0.1 mg kg(-1)) (P < 0.05). Folic acid deficiency (0.1 mg kg(-1)) up-regulated interleukin 1β, interleukin 8, tumor necrosis factor α, nuclear factor κB p65 (NF-κB p65), IκB kinase α (IKK-α), IKK-β and IKK-γ gene expression, meanwhile down-regulated interleukin 10, transforming growth factor β, IκB and target of rapamycin gene expression in the PI, MI and DI (P < 0.05). These data suggested that folic acid deficiency decreased fish intestinal innate immune function may be partly contributed to the regulation of NF-κB p65 pathway. Moreover, the activities and corresponding gene expression of glutathione content, Cu/Zn superoxide dismutase, catalase, glutathione peroxidase, glutathione s-transferases and glutathione reductase in fish intestine were depressed by deficient folic acid diet (0.1 mg kg(-1)) (P < 0.05). Furthermore, folic acid deficiency (0.1 mg kg(-1)) down-regulated NF-E2-related factor 2 (Nrf2) gene expression, up-regulated Kelch-like-ECH-associated protein 1a (Keap1a) and Keap1b gene expression in fish intestine (P < 0.05). These data indicated that deficient folic acid diet damaged fish intestinal antioxidant capacity partly by regulating Nrf2/Keap1 pathway. Additionally, folic acid deficiency (0.1 mg kg(-1)) down-regulated claudin-b, claudin-c, claudin-3, occludin and zonula occludens 1 gene expression; whereas folic acid deficiency (0.1 mg kg(-1)) up-regulated claudin-12, claudin-15, myosin light chain kinase (MLCK) and p38 mitogen activated protein kinase (p38 MAPK) gene expression in the PI, MI and DI (P < 0.05), suggesting that folic acid deficiency may damage fish intestinal tight junctions associated with the mediation of MLCK and p38 MAPK gene expression. In conclusion, folic acid deficiency (0.1 mg kg(-1)) impaired fish intestinal immunity, antioxidant capacity and tight junctions.

Early life perfluorooctanesulphonic acid (PFOS) exposure impairs zebrafish organogenesis

As a persistent organic contaminant, perfluorooctanesulphonic acid (PFOS) has been widely detected in the environment, wildlife, and humans. The present study revealed that zebrafish embryos exposed to 16 μM PFOS during a sensitive window of 48-96 hour post-fertilization (hpf) disrupted larval morphology at 120 hpf. Malformed zebrafish larvae were characterized by uninflated swim bladder, less developed gut, and curved spine. Histological and ultrastructural examination of PFOS-exposed larvae showed structural alterations in swim bladder and gut. Whole genome microarray was used to identify the early transcripts dysregulated following exposure to 16 μM PFOS at 96 hpf. In total, 1278 transcripts were significantly misexpressed (p<0.05) and 211 genes were changed at least two-fold upon PFOS exposure in comparison to the vehicle-exposed control group. A PFOS-induced network of perturbed transcripts relating to swim bladder and gut development revealed that misexpression of genes were involved in organogenesis. Taken together, early life stage exposure to PFOS perturbs various molecular pathways potentially resulting in observed defects in swim bladder and gut development.

Nutritional management of acute pancreatitis in dogs and cats

OBJECTIVE

To review current and emerging nutritional approaches in the management of acute pancreatitis (AP) in people, dogs, and cats, and to provide a framework for further investigation in this field.

DATA SOURCES

Veterinary retrospective studies and reviews, human prospective clinical trials and reviews, and experimental animal studies focusing on nutritional management during AP.

SUMMARY

Nutritional management is an important part of the treatment plan for patients with AP. In human medicine, the general approach for providing nutrition in patients with AP has changed in recent years and favors enteral over parenteral nutrition with an emphasis on early enteral nutrition (EN). Although there are limited data available, there is increasing evidence in the veterinary literature that supports the beneficial role of EN in AP and contradicts previous assumptions about poor tolerance to enteral feeding in this patient population. Parenteral nutrition may be appropriate alone or in combination with EN as a temporary measure in malnourished patients that do not tolerate adequate EN; however, enteral feeding should be attempted first in most cases. Immunonutrition is being investigated for its positive role in modulating pancreatic inflammation and improving gut barrier function in cases of human AP.

CONCLUSIONS

The nutritional management of veterinary patients with AP remains challenging. Based on clinical evidence in people, experimental animal studies, and preliminary studies in dogs and cats, the choice of EN over parenteral nutritional support during AP in dogs and cats appears to be beneficial and well tolerated. Optimization of nutritional therapies in dogs and cats including the use of immunonutrition during AP warrants further investigation.

Detection of intestinal intraepithelial lymphocytes, goblet cells and secretory IgA in the intestinal mucosa during Newcastle disease virus infection

Newcastle disease, which is caused by Newcastle disease virus (NDV), is a highly contagious viral disease of poultry and other bird species. The mucosa is the first line of defence to invading pathogens, including NDV, and it has been confirmed that the mucosa can contribute to host protection. This study was conducted to evaluate the intestinal mucosal immunology in NDV infection. Forty specific-pathogen-free chickens were divided into two groups, 20 birds in each group. Group 1 was inoculated with NDV by the intravenous route. Group 2 was used as the control group and was given sterile phosphate-buffered saline by the same route. At 24, 48, 72, and 96 h post infection (h.p.i.), five chickens from each treatment were killed. Samples of the duodenum, jejunum, and ileum were collected to quantify intestinal intraepithelial lymphocytes (IEL), goblet cells and secretory IgA (sIgA) by cytochemistry and immunohistochemistry analysis. The results indicated that IEL were increased from 24 to 72 h.p.i. in the infected tissues, and were significantly higher than in the control group at 48 h.p.i. (P < 0.01). In contrast to IEL, goblet cell numbers were reduced dramatically from 24 to 96 h.p.i. in the infected birds (P < 0.01) Furthermore, the content of sIgA was significantly higher at 48 and 72 h.p.i. in the infected tissues (P < 0.01). sIgA positivity was observed in the epithelial lining of the intestinal mucosa. These data suggest that IEL, goblet cells, and sIgA were involved in the intestinal mucosal immunity against NDV infection.

JAK-STAT and intestinal mucosal immunology

The intestinal mucosal immune system is challenged with bacteria, viruses, and parasites, in addition to food and environmental antigens, that require dynamic immune responsiveness for homeostasis. One central signaling pathway is JAK-STAT, which regulates the adaptive and innate immune arms of mucosal immunity as well as epithelial repair and regeneration. Adaptive immunity includes lymphocyte mediated secretion of specific antibodies, while innate immune respones include secretion of non-antigen specific compounds. This review examines effects of specialized nutrition support on JAK-STAT in innate immune function and in lymphocyte modulation and epithelial antibody transport in gut-associated lymphoid tissue.

Nutritional support in acute pancreatitis

Acute pancreatitis can present as a mild or severe disease. Most patients have a mild disease and recover without requiring nutritional support. Patients with severe acute pancreatitis may develop systemic inflammatory response syndrome and progress to multi-organ failure. These ill patients have high metabolism and protein catabolism. Hence, the nutritional management of these patients can be challenging. The aim of nutritional support is to meet the elevated metabolic demands as far as possible without stimulating pancreatic secretion and yet maintaining the gut integrity. The concept of pancreatic rest has evolved over the years. To date, there is a substantial scientific proof that enteral nutrition (EN) in comparison to parenteral nutrition significantly reduces infectious complications, surgical interventions and mortality in predicted severe acute pancreatitis. EN may be able to improve outcome in these patients if given early. In this review, we summarized the current knowledge on nutrition in acute pancreatitis and shared our local experience.

Evaluation of early enteral feeding through nasogastric and nasojejunal tube in severe acute pancreatitis: a noninferiority randomized controlled trial

OBJECTIVE

This study aimed to determine the noninferiority of early enteral feeding through nasogastric (NG) compared to nasojejunal (NJ) route on infectious complications in patients with severe acute pancreatitis (SAP).

METHODS

Patients with SAP were fed via NG (candidate) or NJ (comparative) route. The primary outcome was the occurrence of any infectious complication in blood, pancreatic tissue, bile, or tracheal aspirate. Secondary end points were pain in refeeding, duration of hospital stay, intestinal permeability assessed by lactulose/mannitol excretion, and endotoxemia assessed by endotoxin core antibody types immunoglobulin G and M.

RESULTS

Seventy-eight patients were randomized to feeding by either the NG or the NJ route. During the hospital stay, the presence of any infectious complication in the NG and NJ groups was 23.1% and 35.9% (significantly different), respectively. The effect size of the difference of infectious complications was -12.8 (95% confidence interval, -29.6 to 4.0). The upper limit of the 95% confidence interval was 4.0 and was within the 5% limit set for noninferiority. The value of 8.0 for the number needed to treat implies that 8 patients should be treated with NG compared with the NJ group to prevent 1 patient from any of the infectious complications.

CONCLUSIONS

Early enteral feeding through NG was not inferior to NJ in patients with SAP. Infectious complications were within the noninferiority limit. Pain in refeeding, intestinal permeability, and endotoxemia were comparable in both groups.

Delayed enteral feeding impairs intestinal carbohydrate absorption in critically ill patients

OBJECTIVES

Delay in initiating enteral nutrition has been reported to disrupt intestinal mucosal integrity in animals and to prolong the duration of mechanical ventilation in humans. However, its impact on intestinal absorptive function in critically ill patients is unknown. The aim of this study was to examine the impact of delayed enteral nutrition on small intestinal absorption of 3-O-methyl-glucose.

DESIGN

Prospective, randomized study.

SETTING

Tertiary critical care unit.

PATIENTS

Studies were performed in 28 critically ill patients.

INTERVENTIONS

Patients were randomized to either enteral nutrition within 24 hrs of admission (14 "early feeding": 8 males, 6 females, age 54.9 ± 3.3 yrs) or no enteral nutrition during the first 4 days of admission (14 "delayed feeding": 10 males, 4 females, age 56.1 ± 4.2 yrs).

MEASUREMENTS AND MAIN RESULTS

Gastric emptying (scintigraphy, 100 mL of Ensure (Abbott Australia, Kurnell, Australia) with 20 MBq Tc-suphur colloid), intestinal absorption of glucose (3 g of 3-O-methyl-glucose), and clinical outcomes were assessed 4 days after intensive care unit admission. Although there was no difference in gastric emptying, plasma 3-O-methyl-glucose concentrations were less in the patients with delayed feeding compared to those who were fed earlier (peak: 0.24 ± 0.04 mmol/L vs. 0.37 ± 0.04 mmol/L, p < .02) and integrated (area under the curve at 240 mins: 38.5 ± 7.0 mmol/min/L vs. 63.4 ± 8.3 mmol/min/L, p < .04). There was an inverse correlation between integrated plasma concentrations of 3-O-methyl-glucose (area under the curve at 240 mins) and the duration of ventilation (r = -.51; p = .006). In the delayed feeding group, both the duration of mechanical ventilation (13.7 ± 1.9 days vs. 9.2 ± 0.9 days; p = .049) and length of stay in the intensive care unit (15.9 ± 1.9 days vs. 11.3 ± 0.8 days; p = .048) were greater.

CONCLUSIONS

In critical illness, delaying enteral feeding is associated with a reduction in small intestinal glucose absorption, consistent with the reduction in mucosal integrity after nutrient deprivation evident in animal models. The duration of both mechanical ventilation and length of stay in the intensive care unit are prolonged. These observations support recommendations for "early" enteral nutrition in critically ill patients.

Supportive care of a critically ill child

The goal of pediatric intensive care is early identification, severity assessment and resuscitation of critical patients by utilizing standardized protocols. The primary or precipitating disorder should be the focus of attention and specific intervention. But in order to provide holistic care to a patient, due attention should also be rendered to supportive care. Monitoring of sick children in PICU is an essential part of management. Various monitoring technologies add to the clinical monitoring but cannot replace clinical monitoring. The treating team should follow a checklist to ensure all aspects of supportive care are taken care of in every patient. Due attention should be paid to glucose control, skin and eye care, oral hygiene, prevention of stress ulcer, care of various lines and catheters and prevention of nosocomial infections.

Lipopolysaccharide induces alteration of serotonin transporter in human intestinal epithelial cells

Intestinal serotoninergic activity and serotonin transporter (SERT) function have been shown to be altered in intestinal inflammatory diseases. Serotonin (5-HT) plays a critical role in the regulation of gastrointestinal physiology. Activity of 5-HT depends on its extracellular availability, partly modulated by SERT that transports 5-HT into the cell. Lipopolysaccharide (LPS) is a component of Gram-negative bacteria outer membrane, which acts as a potent activator of the inflammatory system in the intestine. The aim of this work was to determine, in the enterocyte-like cell line Caco-2, whether LPS treatment affects serotoninergic activity by acting on SERT. The results demonstrate that LPS treatment diminishes SERT activity in a dose- and period-dependent way. The kinetic study shows that V(max) was significantly reduced after treatment with LPS. The LPS effect on 5-HT uptake was, in part, mediated by protein kinase C (PKC) activation. The molecular expression of SERT revealed that LPS treatment did not affect the mRNA level or the SERT protein content in cell homogenate. The level of SERT protein, however, was reduced on brush border membrane. The LPS effect might be due to an alteration of the intracellular traffic of SERT which may, in part, be mediated by PKC activity.

Supplementing suckling rats with whey protein concentrate modulates the immune response and ameliorates rat rotavirus-induced diarrhea

Group A rotaviruses (RV) are the most common causative agents of acute gastroenteritis in children <2 y. The present study was designed to establish the effect of a bovine whey protein concentrate (WPC) in a RV infection model in suckling rats. From d 3 of life, suckling Lewis rats received daily supplements of WPC, WPC plus lactoferrin (LF), standard infant formula (SIF), or water (RV-infected group and an untreated, uninfected reference group). On d 8 of life, heterologous simian RV SA-11 was inoculated orally in the WPC-RV, WPC+LF-RV, SIF-RV, and RV groups. WPC and WPC+LF reduced diarrhea incidence from approximately 90% in RV group to approximately 60% in WPC-RV and WPC+LF-RV groups (P < 0.05), whereas the area under the curve (AUC) of severity along time diminished from approximately 10 AUC in the RV group to approximately 6 AUC in both supplemented groups (P < 0.05). Serum levels of anti-RV antibodies, splenocyte proliferation, and interferon-gamma secretion after specific stimulation were significantly lower in the WPC-RV and WPC+LF-RV groups than in the SIF-RV and RV groups. In the intraepithelial intestinal compartment, RV infection increased the proportion of typical mucosal T cells (IE-T CD8alphaalpha+); however, this modification was controlled by WPC and WPC+LF supplementation. In general, for most of the parameters studied, the SIF-RV and RV groups did not differ. In summary, daily supplementation with WPC or WPC+LF in early life considerably reduces the severity of RV-induced acute gastroenteritis and modulates the immune response against the pathogen.

Effect of CVT-E002 (COLD-fX) versus a ginsenoside extract on systemic and gut-associated immune function

CVT-E002 (sold commercially as COLD-fX) is a patented, polysaccharide-rich extract of North American ginseng (Panax quinquefolium) with purported beneficial effects on influenza and the common cold, although its mechanism of action is largely unknown. This study was conducted to determine the effects of feeding CVT-E002 versus a ginsenoside-containing extract on systemic and gut-associated immune function. For 7 days, male weanling Sprague-Dawley rats (n=10/group) were fed one of four diets: control, low CVT-E002 (450 mg/kg), high CVT-E002 (900 mg/kg), or ginsenoside (450 mg/kg). Lymphocytes were isolated from spleen, mesenteric lymph nodes and Peyer's patches, and immune cell proportions and cytokine production were measured. IgA-positive cells in the jejunum were also assayed. CVT-E002 consumption (particularly at the higher dose) decreased spleen IL-2 and IFN-gamma production following ConA and/or LPS stimulation for 24 or 48 h (P<0.05). Also, CVT-E002-fed rats had a lower proportion of total CD3+ cells and activated T cells (P<0.05). After 48 h of ConA stimulation, spleen IL-1beta production was higher (P<0.05) for animals fed the high dose CVT-E002, whereas TNF-alpha production did not differ significantly from the control group. Feeding the ginsenoside diet resulted in lower (P<0.05) spleen IL-2 production, but the IFN-gamma, TNF-alpha and IL-1beta response to ConA was not different from control animals at 48 h. A higher proportion of jejunal IgA-positive cells was found in rats fed the ginsenoside diet (P<0.05). In conclusion, feeding CVT-E002 modifies systemic immune responses and appears to affect gut-associated immunity in a manner distinct from that of ginsenoside-containing extracts of North American ginseng.

The impact of delaying enteral feeding on gastric emptying, plasma cholecystokinin, and peptide YY concentrations in critically ill patients

BACKGROUND

Enteral nutrient (EN) deprivation slows gastric emptying (GE) and increases plasma cholecystokinin (CCK) concentrations in healthy humans and may potentially contribute to the delayed GE in the critically ill. This study examined the impact of delayed feeding on GE, plasma CCK, and peptide YY (PYY) concentrations in the critically ill.

DESIGN

Randomized controlled trial.

SETTING

Mixed medical and surgical intensive care unit (ICU).

INTERVENTIONS

Twenty-eight critically ill patients were randomized to receive EN either within 24 hrs of admission ("early feeding": 54.9 +/- 3.3 yrs; Acute Physiology and Chronic Health Evaluation (APACHE) II = 23.0 +/- 1.8) or on day 4 of admission after GE assessment ("delayed feeding": 56.1 +/- 4.2 yrs, APACHE II = 21.7 +/- 1.8). GE of 100 ml of Ensure was measured using scintigraphy on day 4 of admission. Blood was sampled for measurement of plasma CCK, PYY, and glucose concentrations.

RESULTS

Demographics, APACHE II score, use of inotrope and morphine sedation were similar between the groups. The mean administered/prescribed caloric ratio in the "early feeding" group was 72 +/- 4%. There were no differences in the retention of meal, intragastric meal distribution, proportion of patients with delayed GE (9/14 vs. 9/14), and plasma CCK and PYY concentrations during fasting and postprandially between the two groups. There was no relationship between the number of calories received and percentage of meal retention at 240 min (p > .05). However, delayed feeding was associated with longer duration of mechanical ventilations (13.7 +/- 1.9 vs. 9.2 +/- .9 days, p = .049) and length of stay in ICU (15.9 +/- 1.9 vs. 11.3 +/- 0.8 days, p = .048), but no difference in mortality.

CONCLUSIONS

In critical illness, delayed enteral feeding appears to have little impact on either GE or the enterogastric feedback hormones. However, the association between delayed feeding and increased duration of ventilation and length of stay in the ICU supports the current recommendation that enteral nutrition should be commenced early.

Bovine whey protein concentrate supplementation modulates maturation of immune system in suckling rats

During neonatal life, challenges from breast milk and microbial flora promote immune system maturation. Immunonutrition in these stages may become an important way to increase natural defence systems. The aim of this study was to determine the effect of a daily bovine milk whey protein concentrate (WPC) supplement on the intestinal and systemic immune systems in suckling rats. The composition of intraepithelial and lamina propria lymphocytes (IEL and LPL) was analysed by flow cytometry. Systemic and intestinal humoral immune responses were determined by sera Ig levels and Ig-secreting cell quantification by ELISA and ELISPOT, respectively. From birth, suckling Wistar rats were supplemented with WPC or standard infant formula (SIF). The WPC group showed the same proportion of most of the main mucosal cell subsets as the reference animals. However, in the first days of life WPC enhanced the innate immunity by increasing the NK cell proportion in both epithelial and lamina propria (LP) compartments. A rise in intestinal CD8alphaalpha+ IEL was also induced by WPC supplementation. A time-course of sera Ig levels and spontaneous IgA, IgM and IgG production by LPL and mononuclear cells from blood and spleen, in the WPC group, exhibited a similar pattern to those pups fed only by dam's milk. In summary, the present results show the effects of WPC on enhancing mucosal innate immunity during early life.

Small bowel endoscopic enteral access

The use of small bowel access for small intestinal delivery of enteral nutrition is becoming more common. Patients at risk for gastric regurgitation and aspiration, gastric intolerance, and pancreatitis are some of the classic patient groups for which small bowel feedings may be necessary. The endoscopist should have command of all forms of endoscopic small bowel enteral access, including nasojejunal tube placement, percutaneous gastro/jejunostomy, and direct percutaneous jejunostomy. Knowledge of not only the procedure techniques, but also the potential complications, is imperative to achieving good clinical outcomes.

The immune-enhancing effects of dietary fibres and prebiotics

The gastrointestinal tract is subjected to enormous and continual foreign antigenic stimuli from food and microbes. This organ must integrate complex interactions among diet, external pathogens, and local immunological and non-immunological processes. It is critical that protective immune responses are made to potential pathogens, while hypersensitivity reactions to dietary antigens are minimised. There is increasing evidence that fermentable dietary fibres and the newly described prebiotics can modulate various properties of the immune system, including those of the gut-associated lymphoid tissues (GALT). This paper reviews evidence for the immune-enhancing effects of dietary fibres. Changes in the intestinal microflora that occur with the consumption of prebiotic fibres may potentially mediate immune changes via: the direct contact of lactic acid bacteria or bacterial products (cell wall or cytoplasmic components) with immune cells in the intestine; the production of short-chain fatty acids from fibre fermentation; or by changes in mucin production. Although further work is needed to better define the changes, mechanisms for immunomodulation, and the ultimate impact on immune health, there is convincing preliminary data to suggest that the consumption of prebiotics can modulate immune parameters in GALT, secondary lymphoid tissues and peripheral circulation. Future protocols on the physiological impact of consuming prebiotics should be designed to include assessments of the gut microflora, gut physiology and the function and composition of the various regions of GALT.

Nutrition support in acute pancreatitis

The benefit of early enteral nutrition (EN) for the disease process and for patient outcome in severe acute pancreatitis is dramatic. A narrow window of opportunity exists during which there is potential for EN to decrease disease severity and reduce overall complications. Most patients with severe pancreatitis tolerate enteral feeds. Any signs of symptom exacerbation or increasing inflammation in response to EN may be ameliorated by subtle adjustments in the feeding strategy. In this manner, provision of EN represents primary therapy in the management of the patient with acute pancreatitis and is emerging as the gold standard of therapy in nutrition support for this disease process.

Aldose reductase regulates TNF-alpha-induced PGE2 production in human colon cancer cells

Pro-inflammatory cytokines such as TNF-alpha play an important role in the pathophysiology of diseases such as Crohn's and ulcerative colitis which cause increased risk of colorectal cancer. However, the mechanisms underlying colon carcinogenesis are not well understood. Herein we report that inhibition/antisense abolition of polyol pathway enzyme, aldose reductase (AR) inhibited the TNF-alpha-induced synthesis of prostaglandin E2 and the activity of cyclooxygenase (Cox) in human colon cancer cells, Caco-2. Inhibition of AR prevented TNF-alpha-induced activation of PKC and NF-kappaB which resulted in the abrogation of Cox-2 mRNA and protein expression. These results suggest that inhibition of AR could be a novel chemopreventive approach to colon cancer.

Oral carbohydrate solution ameliorates endotoxemia-induced splanchnic ischemia

The purpose of this study was to investigate the effect of oral administration of a simple carbohydrate solution on splanchnic circulation and bacterial translocation in endotoxemia. Group 1 was sham control; group 2 was starved for 24 hours; in group 3, endotoxin was administrated at the end of starvation; in group 4, carbohydrate solution was administrated via orogastric route for 24 hours; and in group 5, carbohydrate solution was given and endotoxin was administrated at the end of 24 hours. Splanchnic blood flows were recorded and tissue samples were collected for microbiological analyses. There was a significant increase (P<.05) in the incidence of bacterial translocation in starvation. Endotoxemia decreased distal (P=.021) and midmesenteric (P=.046) flow in starved animals. Oral carbohydrate significantly increased ileal blood flow in starvation (P=.036) and endotoxemia (P=.008). In conclusion, oral carbohydrate solution prevents bacterial translocation during starvation and endotoxemia. The possible mechanism is the improvement in the mesenteric blood flow.

The effects of undernutrition and refeeding on metabolism and digestive function

PURPOSE OF REVIEW

An intimate interrelationship exists between nutritional status and gut function. This review focuses on the consequences of a poor nutritional state on metabolism and digestive function, and evaluates the effects of refeeding.

RECENT FINDINGS

Severe undernutrition has been associated with increased fat and protein catabolism, reflected by a decreased respiratory quotient. Resting energy expenditure assessed in relationship to body weight was increased, probably as a consequence of changes in body composition. Protein synthesis, expressed per kg body weight, was decreased in undernourished patients with coexistent disease, but not in anorexia nervosa patients, indicating the detrimental effects of disease states. Severe undernutrition is associated with malabsorption, which improves following refeeding. Despite a high prevalence of villous atrophy in the duodenal mucosa in undernourished patients, mucosal protein fractional synthesis rates appeared normal. Refeeding resulted in a potent trophic response, and normalization of the mucosal morphology. Gastric and pancreatic secretion was significantly impaired by the undernourished state, with significant improvement following refeeding.

SUMMARY

Undernutrition is associated with impairment of digestive function, which is likely to further aggravate the nutritional state. Refeeding corrects this dysfunction, and results in disruption of this vicious circle.

Early enteral administration of immunonutrition in critically ill children: results of a blinded randomized controlled clinical trial

OBJECTIVES

In a blinded, prospective, randomized, controlled clinical trial, we compared nitrogen balance (NB), nutritional indices, antioxidant catalysts, and outcome in critically ill children given an immune-enhancing formula (I) or conventional early enteral nutrition (C).

METHODS

Fifty patients, 103 +/- 7 months old, with disorders prompting admission to the pediatric intensive care unit, including sepsis, respiratory failure, and severe head injury, were enrolled in the study. Within 12 h of admission, patients were randomized to receive I (n=25) or C (n=25). Caloric intake was aimed at meeting patient's predicted basal metabolic rate by day 2 and predicted energy expenditure by day 4, irrespective of group assignment. Outcome endpoints and complications were recorded; NB, transthyretin, retinol-binding protein, transferrin, zinc, copper, and metabolic indices were measured on days 1 and 5 and compared with clinical and nutritional characteristics within and between groups.

RESULTS

Both diets achieved their initial targets of covering predicted basal metabolic rate by day 2 and predicted energy expenditure by day 4. Twenty four-hour NB became positive in 40% of patients in group C and occurred in 64% of patients in group I by day 5. Only in group I did the mean NB become positive by day 5 (0.07+/-0.07 g/kg versus -0.24+/-0.03 g/kg on day 1, P<0.001) compared with group C in which the mean NB remained negative (-0.06+/-0.04 g/kg versus -0.25+/-0.06 g/kg on day 1, P<0.001). By day 5, nutritional indices and antioxidant catalysts showed a higher increasing trend in group I compared with group C and higher osmolality (P<0.02), sodium (P<0.03), and urea (P<0.04). Diarrhea for group I (P<0.02) and gastric distention for group C (P<0.04) were the most frequently recorded complications. Mortality or length of stay did not differ between groups, but there was a trend for less gastric gram plus isolates (P<0.05) or for Candida species (P<0.04) and nosocomial infections in group I compared with group C.

CONCLUSIONS

Although less well tolerated, immunonutrition is a feasible method of early enteral nutrition in the pediatric intensive care unit. It has a favorable effect on nutritional indices and antioxidant catalysts, but not on outcome hard endpoints. Although it poses a higher metabolic burden to the patient, it shows a trend to improve colonization and infection rates. Appropriate modifications for specific age populations might improve its tolerability and benefits among critically ill children.

The effect of protective nutrients on mucosal defense in the immature intestine

Oral nutrition plays a dual role in the gut, providing nutrition to the body while affecting the function of the gastrointestinal tract. The exposure of the gut to food antigens, in the form of either beneficial or harmful nutritional substances, contributes to a vast array of physiological and pathologic gastrointestinal responses with secondary systemic implications. The immune system of the gastrointestinal tract is always involved in the first line of defense, and its actions are particularly important in the early period of life as maturation takes place. From maturation, a balance ensues in the regulatory mechanism of host defense, ultimately leading to either tolerance or immune reaction. This paper emphasizes how some nutrients may beneficially affect the gastrointestinal immune system's maturation in both term and especially premature neonates.

Gastric vs small-bowel feeding in critically ill children receiving mechanical ventilation: a randomized controlled trial

STUDY OBJECTIVES

To determine the effect of feeding tube position (gastric vs small bowel) on adequacy of nutrient delivery and feeding complications, including microaspiration, in critically ill children.

DESIGN

Randomized controlled trial.

SETTING

Pediatric ICU in a university teaching hospital.

PATIENTS

Seventy-four critically ill patients < 18 years of age receiving mechanical ventilation were randomized to receive gastric or small-bowel feeding.

INTERVENTIONS

All feeding tubes were inserted at the bedside. Color, pH, and bilirubin concentration of the feeding tube aspirates were used to guide placement. Final tube position was confirmed radiographically. Continuous feedings were advanced to achieve a caloric goal based on age and body weight. Tracheal secretions were collected daily and tested for gastric pepsin by immunoassay.

MEASUREMENTS AND RESULTS

Thirty-two patients were randomized to the gastric group, and 42 patients were randomized to the small-bowel group. Twelve patients exited the study because a small-bowel tube could not be placed at the bedside, leaving 30 patients in the small-bowel group. Gastric and small-bowel groups were similar at baseline in age, sex, percentage of ideal body weight, serum prealbumin concentration, and pediatric risk of mortality score. The percentage of daily caloric goal achieved was less in the gastric group compared to the small-bowel group (30 +/- 23% vs 47 +/- 22%, p < 0.01). No difference was found in the proportion of tracheal aspirates positive for pepsin between the gastric and small-bowel groups (50 of 146 aspirates vs 50 of 172 aspirates, respectively; p = 0.3). No differences were found in the frequency of feeding tube displacement, abdominal distension, vomiting, or diarrhea between groups.

CONCLUSIONS

Small-bowel feeds allow a greater amount of nutrition to be successfully delivered to critically ill children. Small-bowel feeds do not prevent aspiration of gastric contents.

Failure of the gut barrier system enhances liver injury in rats: protection of hepatocytes by gut-derived hepatocyte growth factor

OBJECTIVE

Clinical and experimental studies suggest that impairment of the mucosal barrier system increases gut-derived endotoxin in the portal blood, which causes liver injury. The aim of this study was to elucidate the mechanism of liver injury caused by gut defence failure.

DESIGN

Wistar rats were administered either enteral lipopolysaccharide (LPS) or LPS via the portal vein.

METHODS

Blood samples were collected via the inferior vena cava at necropsy. Serum aspartate transaminase (AST) and alanine transaminase (ALT) were analysed by standard enzymatic procedures and cytokines [tumour necrosis factor-alpha, interleukin (IL)-1beta, interferon-gamma, IL-6 and hepatocyte growth factor (HGF)] were measured by enzyme-linked immunosorbent assay. Livers were removed and snap-frozen in liquid nitrogen. CD14, CD68, Toll-like receptor (TLR) 2, TLR4 and Fas ligand (FasL) were analysed immunohistochemically. Expression of TLR2, TLR4 and CD14 mRNA was determined by reverse transcriptase-polymerase chain reaction.

RESULTS

In enterally-treated rats, AST and ALT were not increased and cytokine levels were under the limits of detection in the absence of a rise in HGF. Enteral administration of LPS increased HGF dose-dependently. Injection of LPS in the portal vein resulted in significant increases in AST, ALT, tumour necrosis factor-alpha, IL-1beta, interferon-gamma and IL-6 levels, but no change in HGF levels. Immunohistochemical analysis revealed that intraportal LPS administration increased CD14, TLR4, CD68 and FasL. Reverse transcriptase-polymerase chain reaction analysis demonstrated that TLR4 mRNA expression was upregulated 0.5 h after intraportal LPS administration.

CONCLUSION

s Our data suggest that Kupffer cell activation mediated by intraportal LPS via TLR4 is involved in liver injury, possibly through both tumour necrosis factor-alpha/IL-1beta and FasL, and that lack of HGF activity in the impaired gut could not counteract liver injury.

Observations on aggregated lymphoid nodules in the cardiac glandular areas of the Bactrian camel (Camelus bactrianus)

Aggregated lymphoid nodules are an important part of the gut-associated lymphoid tissue (GALT). They are mainly distributed in the ileum and appendix of animals and humans but their distribution in the cardiac glandular area has not been reported. A study of stomach histology in the Bactrian camel has revealed that the nodules are distributed as a band-like region along the ventral wall of the stomach neck, at the beginning of the cranial enlargement and on the lesser curvature. The mucous folds are thicker in these regions than where there are no aggregated lymphoid nodules. The nodules appeared similar to ileal aggregated lymphoid nodules found in other animals and consisted of typical polymorphological lymphatic nodules arranged in a single continuous row occupying the submucosa and forming mucosal folds together with the mucous membrane. The whole mucous membrane with cardiac glands, diffuse lymphatic tissue and solitary lymphoid nodules in the lamina propria were found to cover the aggregated lymphoid nodule regions, but some nodules with a typical corona extended into the lamina propria and were covered with follicle-associated epithelium devoid of cardiac glands. These findings indicate that the stomach of the Bactrian camel possesses not only a special structure of digestion but also has characteristic immunological morphology.

Gamma interferon augments the intracellular pathway for lipopolysaccharide (LPS) recognition in human intestinal epithelial cells through coordinated up-regulation of LPS uptake and expression of the intracellular Toll-like receptor 4-MD-2 complex

Although some intestinal epithelial cell lines are known to respond to lipopolysaccharide (LPS), understanding of the relationship between LPS responsiveness and the expression of LPS receptors or factors regulating LPS responsiveness of intestinal epithelial cell lines is incomplete. In this study, we demonstrate that commonly studied human intestinal epithelial cell lines can be classified into at least three different types on the basis of LPS responsiveness, Toll-like receptor-4 (TLR4) expression, and the effects of gamma interferon (IFN-gamma) on LPS responsiveness. The first phenotype, which includes the HCT-116 and Caco-2 cell lines, is characterized by relative hyporesponsiveness to LPS and diminished expression of TLR4 protein. In these cells, IFN-gamma does not induce LPS responsiveness. The second phenotype, which includes cell line SW480, exhibits a highly LPS-responsive phenotype and surface expression of TLR4 protein even in unprimed conditions. These lines are functionally similar to cells of monocytic lineage. In the third phenotype, which includes the HT-29 and Colo205 cell lines, TLR4 protein is largely present in the cytoplasmic fraction and the cells are hyporesponsive to LPS in an unprimed condition. However, priming of these cells with IFN-gamma can induce LPS responsiveness through augmentation of LPS uptake and expression of MD-2 mRNA and intracellular TLR4 proteins. Finally, these findings suggest that the Th1 cytokine IFN-gamma modulates LPS responsiveness through several mechanisms in intestinal epithelial cells and that these cells may comprise different subpopulations with distinct roles in innate immune responses.

Membrane peroxidation by lipopolysaccharide and iron-ascorbate adversely affects Caco-2 cell function: beneficial role of butyric acid

BACKGROUND

Membrane lipid peroxidation may play a role in immune-mediated bowel diseases.

OBJECTIVE

We examined the effects of lipopolysaccharide (LPS), a ubiquitous endotoxin mediator of gram-negative bacteria, alone and in combination with iron-ascorbate, on enterocyte function. Furthermore, we assessed the antioxidant capacity of butylated hydroxytoluene (BHT) and butyric acid, which are known to play a significant role in the welfare of intestinal mucosa.

DESIGN

Differentiated intestinal Caco-2 cells were used to study the induction of membrane peroxidation by LPS (100 micro g/mL) and iron-ascorbate (0.2 and 2 mmol/L, respectively) and to examine the beneficial effects of BHT and butyric acid.

RESULTS

A significant dose-dependent increase in malondialdehyde, accompanied by lower apical membrane fluidity and significantly decreased sucrase activity, was observed when Caco-2 cells were incubated with LPS. LPS also augmented paracellular permeability ([(14)C]polyethylene glycol flux), prostaglandin E(2) production, and cyclooxygenase-2 (EC 1.14.99.1) expression. These abnormalities were exacerbated by the coadministration of iron-ascorbate, but most of them were suppressed by butyric acid and BHT.

CONCLUSION

Bacterial endotoxin and prooxidants may overwhelm antioxidant defenses and become deleterious to enterocyte function, whereas butyric acid and BHT may provide antioxidant protection.

Epidermal growth factor activation of intestinal glutamine transport is mediated by mitogen-activated protein kinases

Glutamine is an essential nutrient for gut functions, but the regulation of its uptake by intestinal mucosal cells is poorly understood. Given the pivotal role of epidermal growth factor (EGF) in regulating gut metabolism, growth, and differentiation, this in vitro study was designed to investigate the intracellular signaling pathways involved in the regulation of EGF-mediated intestinal glutamine transport in intestinal epithelia. Continuous incubation with EGF (>30 hours, 100 ng/ml) stimulated glutamine transport activity across intestinal epithelial Caco-2 cell apical membrane. Exposure to EGF for 48 hours resulted in an increase in transport activity (50%) and glutamine transport system B gene ATB(0) mRNA levels (ninefold). EGF stimulated glutamine transport activity by increasing the glutamine transporter maximal velocity (V(max)) without altering the transporter apparent affinity (K(m)). Furthermore, EGF stimulated both intracellular protein kinase C and mitogen-activated protein kinase MEK1/2 activities. The EGF-stimulated glutamine transport activity was attenuated individually by the specific protein kinase C inhibitor chelerythrine chloride and the mitogen-activated protein kinase MEK1 inhibitor PD 98059. These data suggest that EGF activates glutamine transport activity across intestinal epithelial membrane via a signaling mechanism that involves activation of protein kinase C and the mitogen-activated protein kinase MEK1/2 cascade. EGF activates glutamine transport via alterations in transporter mRNA levels and the number of functional copies of transporter units.

Association between the C3435T MDR1 gene polymorphism and susceptibility for ulcerative colitis

BACKGROUND & AIMS

The human multidrug resistance 1 (MDR1) gene product P-glycoprotein is highly expressed in intestinal epithelial cells, where it constitutes a barrier against xenobiotics. The finding that mdr1a knockout mice develop a form of colitis that is similar to ulcerative colitis, which can be prevented by antibiotics, indicates a barrier function for P-glycoprotein against the invasion of bacteria or toxins. Because the MDR1 single nucleotide polymorphism C3435T is associated with lower intestinal P-glycoprotein expression, we tested whether this polymorphism predisposes to development of ulcerative colitis.

METHODS

Allele frequencies and genotype distributions of the C3435T single nucleotide polymorphism were investigated in 149 patients with ulcerative colitis, 126 patients with Crohn's disease, and sex-matched healthy controls.

RESULTS

Significantly increased frequencies of the 3435T allele and the 3435TT genotype were observed in patients with ulcerative colitis compared with controls (3435T: P = 0.049; odds ratio, 1.4; 95% confidence interval, 1.02-1.94; 3435TT: P = 0.045; odds ratio, 2.03; 95% confidence interval, 1.04-3.95). In contrast, frequencies of the T allele and the TT genotype were the same in patients with Crohn's disease as in controls (P = 0.66 and P = 0.59, respectively). In comparison to 998 non-sex-matched controls, the effect for the TT genotype in ulcerative colitis patients was more pronounced (P = 0.0055; odds ratio, 2.1).

CONCLUSIONS

The higher frequency of the 3435TT genotype in patients with ulcerative colitis corroborates the findings from the mdr1a knockout mice. The results support the notion that P-glycoprotein plays a major role in the defense against intestinal bacteria or toxins. Impairment of barrier function in 3435TT subjects could render this genotype more susceptible to the development of ulcerative colitis.

Protein kinase C activation of intestinal glutamine transport is mediated by mitogen-activated protein kinases

BACKGROUND

Glutamine is essential for the preservation of intestinal structure and function and its uptake by the bowel is augmented during catabolic states. However, the signal transduction pathways implicated in brush border glutamine transport have not been examined. The aim of this study was to investigate the intracellular signaling pathways involved in the regulation of accelerated intestinal glutamine transport. Our hypothesis was that the activation of intestinal glutamine transport involves protein kinase C (PKC) and is mediated by mitogen-activated protein kinases (MAPKs).

METHODS

[3H]L-Glutamine (50 microM) transport activity and mRNA levels for the intestinal glutamine transporter ATB(0) were measured in intestinal epithelial Caco-2 cells. Confluent cells were treated with phorbol ester (PMA, 0-10 microM), the MAPK MEK inhibitor PD 98059 (0-100 microM), actinomycin (0-0.1 microM), MAPK p38 inhibitor SB 203580 (0-10 microM), protein kinase C inhibitor chelerythrine chloride (0-6.6 microM), or cycloheximide (0-10 microM) for 24 h. Data were analyzed by ANOVA with significance set at P < 0.05.

RESULTS

Phorbol ester treatment increased intestinal System B glutamine transport activity by 75%, an increase that was blocked individually by PD 98059, chelerythrine chloride, actinomycin, and cycloheximide, but not SB 203580, an effect first noted at 6 h. The resulting activity increase was consistent with de novo synthesis of transporter units and enhanced expression of transporter gene ATB(0) as indicated by a threefold increase of ATB(0) mRNA levels in PMA-treated cells.

CONCLUSIONS

Activation of glutamine transport in Caco-2 cells by phorbol ester occurs via signaling pathways that lead to transcription of the glutamine transporter gene. PKC and mitogen-activate protein kinase MEK are key intracellular mediators involved in this signal transduction cascade.

Persistent fetal circulation

Persistent fetal circulation (PFC), also known as persistent pulmonary hypertension of the newborn, is defined as postnatal persistence of right-to-left ductal or atrial shunting, or both in the presence of elevated right ventricular pressure. It is a relatively rare condition that is usually seen in newborns with respiratory distress syndrome, overwhelming sepsis, meconium and other aspiration syndromes, intrauterine hypoxia and ischemia, and/or neonatal hypoxia and ischemia. This condition causes severe hypoxemia, and, as a result, has significant morbidity and mortality. Improved antenatal and neonatal care; the use of surfactant; continuous monitoring of oxygenation, blood pressure and other vital functions; and early recognition and intervention have made this condition even more rare. In modern neonatal intensive care units, anticipation and early treatment of PFC and its complications in sick newborns are commonplace. Thus, severe forms of PFC are only seen on isolated occasions. Consequently, it is even more imperative to revisit PFC compared with the time when there were occasional cases of PFC seen in neonatal intensive care units, and to discuss evolving treatment and management issues that pertain to this syndrome.

Nutrition and the mucosal immune system

Gut-associated lymphoid tissue is the dominant site for the initiation of mucosal immune response. Mucosal immunity depends on regulatory signals; nutritional elements, including fats, amino acids, and micronutrients, are critical cofactors for these signals. Nutrients specifically affect lymphocyte influx and migration, mononuclear cell activation, and the differentiated expression of immune response. The molecular basis of nutrient action has been shown to involve effects on receptor regulation, adhesion molecule expression, and the pattern of cytokine production. The gastrointestinal mucosal immune system is the major site for host interaction with microbes and provides a barrier against systemic access for food antigens and microbes. Nutrient metabolism has unique and direct impact on the host defense system of gut-associated lymphoid tissue and therefore has potential for widely disseminated impact on systemic immune response.

Nutritional support in sepsis: still skeptical?

The immediate metabolic response to a septic challenge is probably adaptive, meaning that nutritional interference, mainly via the parenteral route, during this early phase of instability can do more harm than good. During the later phases, a gradual increase in enteral nutrition, at the expense of parenteral nutrition, combined with the administration of nutraceuticals such as glutamine and omega-3 fatty acids, can counteract wasting and modulate the complex inflammatory response and immunosuppression associated with sepsis. In these times of scarce resources, there is an urgent need to clearly document the efficacy of immuno/pharmaconutrients, individually and in combination, enterally or parenterally, before proposing them for routine management of septic patients in the intensive care unit.