Intestinal permeability in pediatric gastroenterology

Rhamnose Is Superior to Mannitol as a Monosaccharide in the Dual Sugar Absorption Test: A Prospective Randomized Study in Children With Treatment-Naïve Celiac Disease

BACKGROUND AND AIM

We sought to correlate two different measures of gut permeability [lactulose:mannitol (L:M) and lactulose:rhamnose (L:R)] to the severity of duodenal histopathology in children with and without elevated antibodies to tissue transglutaminase (tTG). A secondary objective was to correlate gut permeability with celiac disease (CD) serology and indices of inflammation and bacterial product translocation.

METHODS

We prospectively randomized children undergoing endoscopy with abnormal (n = 54) and normal (n = 10) concentrations of circulating antibodies to tTG, to either L:M or L:R. Biopsies underwent modified Marsh scoring to measure mucosal injury. Circulating anticore Escherichia coli lipopolysaccharide (LPS) IgG, α-1 acid glycoprotein, LPS-binding protein, and C-reactive protein concentrations were measured by enzyme immunoassays.

RESULTS

Of the 54 cases with positive celiac serology, 31 and 69% had modified Marsh 0/1 scores or ≥3a, respectively. Circulating tTG IgA correlated with the modified Marsh score (p = 0.03). L:R, but not L:M or percent L excreted, differed according to modified Marsh scores (p = 0.01). There was no significant association between any systemic marker of inflammation or gut injury, and modified Marsh scores. Concerningly, most participants had evidence of urinary M before the challenge sugar was administered.

CONCLUSIONS

L:R, but not L:M, is associated with modified Marsh scores in children undergoing small bowel biopsy for suspected CD. Despite increased intestinal permeability, we see scant evidence of systemic exposure to gut microbes in these children. Gut permeability testing with L:R may predict which patients with abnormal celiac serology will have biopsy evidence for celiac disease and reduce the proportion of such patients undergoing endoscopy whose Marsh scores are ≤1. M should not be used as a monosaccharide for permeability testing in children.

Epithelial barrier function properties of the 16HBE14o- human bronchial epithelial cell culture model

The human bronchial epithelial cell line, 16HBE14o- (16HBE), is widely used as a model for respiratory epithelial diseases and barrier function. During differentiation, transepithelial electrical resistance (TER) increased to approximately 800 Ohms × cm², while ¹⁴C-d-mannitol flux rates (J_m) simultaneously decreased. Tight junctions (TJs) were shown by diffusion potential studies to be anion-selective with P_C1/P_Na = 1.9. Transepithelial leakiness could be induced by the phorbol ester, protein kinase C (PKC) activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), and the proinflammatory cytokine, tumor necrosis factor-α (TNF-α). Basal barrier function could not be improved by the micronutrients, zinc, or quercetin. Of methodological significance, TER was observed to be more variable and to spontaneously, significantly decrease after initial barrier formation, whereas J_m did not significantly fluctuate or increase. Unlike the strong inverse relationship between TER and J_m during differentiation, differentiated cell layers manifested no relationship between TER and J_m. There was also much greater variability for TER values compared with J_m. Investigating the dependence of 16HBE TER on transcellular ion conductance, inhibition of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) chloride channel with GlyH-101 produced a large decrease in short-circuit current (I_sc) and a slight increase in TER, but no significant change in J_m. A strong temperature dependence was observed not only for I_sc, but also for TER. In summary, research utilizing 16HBE as a model in airway barrier function studies needs to be aware of the complexity of TER as a parameter of barrier function given the influence of CFTR-dependent transcellular conductance on TER.

Toxicokinetic Studies in Piglets Reveal Age-Related Differences in Systemic Exposure to Zearalenone, Zearalenone-14-Glucoside, and Zearalenone-14-Sulfate

Juveniles are considered as one of the most vulnerable population groups concerning mycotoxins and their modified forms. The weaning stage is a particularly vulnerable period in the life of mammals, reflected in intestinal and immune dysfunction. The current study investigated the toxicokinetic (TK) characteristics of zearalenone (ZEN), zearalenone-14-glucoside (ZEN14G), and zearalenone-14-sulfate (ZEN14S) in weaned (4-week-old) piglets, by means of oral and intravenous administration of equimolar doses, i.e., 331, 500, and 415 μg/kg bodyweight, respectively. Plasma and urine were sampled pre- and post-administration and were quantitatively analyzed for ZEN, ZEN14G, ZEN14S, and in vivo metabolites by liquid chromatography-high-resolution mass spectrometry. Tailor-made TK models were elaborated to process data. A statistical comparison of the results was performed with TK data obtained in a previously reported study in pigs of 8 weeks of age. Additionally, porcine plasma protein binding was determined to support TK findings. The TK results for ZEN, ZEN14G, and ZEN14S, obtained in 4- and 8-week-old pigs, revealed significant age-related differences, based on differences in intestinal permeability, body fat content, gastrointestinal transit time, and biotransformation, with a special emphasis on an increased absorbed fraction of ZEN14G, i.e., 94 vs 61% in 4- compared to 8-week-old pigs. Since the growing pig has been reported to be a suitable pediatric animal model for humans concerning TK processes, these results may contribute to refine the risk assessment concerning modified ZEN forms in juvenile animals and humans.

Direct Implementation of Intestinal Permeability Test in NMR Metabolomics for Simultaneous Biomarker Discovery-A Feasibility Study in a Preterm Piglet Model

Measurement of intestinal permeability (IP) is often used in the examination of inflammatory gastrointestinal disorders. IP can be assessed by measurement of urinary recovery of ingested non-metabolizable lactulose (L) and mannitol (M). The present study aimed to examine how measurements of IP can be integrated in a NMR-based metabolomics approach for a simultaneous quantification of L/M ratio and biomarker exploration. For this purpose, plasma and urine samples were collected from five-day-old preterm piglets (n = 20) with gastrointestinal disorders (subjected to intra-amniotic lipopolysaccharide (LPS, 1 mg/fetus)) after they had been administrated a 5% lactulose and 5% mannitol solution (15 mL/kg). The collected plasma and urine samples were analyzed by ¹H NMR-based metabolomics. Urine L/M ratio measured by ¹H NMR spectroscopy showed high correlation with the standard measurement of the urinary recoveries by enzymatic assays (r = 0.93, p < 0.05). Partial least squares (PLS) regressions and correlation analyses between L/M ratio and NMR metabolomics data revealed that L/M ratio was positively correlated with plasma lactate, acetate and succinate levels and negatively correlated with urinary hippuric acid and glycine. In conclusion, the present study demonstrated that NMR metabolomics enables simultaneous IP testing and discovery of biomarkers associated with an impaired intestinal permeability.

Investigation of age-related differences in toxicokinetic processes of deoxynivalenol and deoxynivalenol-3-glucoside in weaned piglets

Age-related differences in toxicokinetic processes of deoxynivalenol (DON) and deoxynivalenol-3-glucoside (DON3G) were studied. DON3G [55.7 µg/kg bodyweight (BW)] and an equimolar dose of DON (36 µg/kg BW) were administered to weaned piglets (4 weeks old) by single intravenous and oral administration in a double two-way cross-over design. Systemic and portal blood was sampled at different time points pre- and post-administration and plasma concentrations of DON, DON3G and their metabolites were quantified using validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) and liquid chromatography-high-resolution mass spectrometry (LC-HRMS) methods. Data were processed using tailor-made compartmental toxicokinetic (TK) models to accurately estimate TK parameters. Results were statistically compared to data obtained in a previous study on 11-week-old pigs using identical experimental conditions. Significant age-related differences in intestinal and systemic exposure to both DON and DON3G were noted. Most remarkably, a significant difference was found for the absorbed fraction of DON3G, after presystemic hydrolysis to DON, in weaned piglets compared to 11-week-old piglets (83% vs 16%, respectively), assumed to be mainly attributed to the higher intestinal permeability of weaned piglets. Other differences in TK parameters could be assigned to a higher water/fat body ratio and longer gastrointestinal transit time of weaned piglets. Results may further refine current risk assessment concerning DON and DON3G in animals. Additionally, since piglets possibly serve as a human paediatric surrogate model, results may be extrapolated to human infants.

Cow's Milk Protein Allergy in Infancy: A Risk Factor for Functional Gastrointestinal Disorders in Children?

The role and prevalence of cow's milk protein allergy (CMA) in functional gastrointestinal disorders remains unclear. The aim of this review is to update knowledge on the relationship between CMA and functional abdominal pain disorders (FAPDs) in children. Cochrane Database and Pubmed were searched from inception using general and specific terms for CMA and functional gastrointestinal disorders. CMA is reported as a predisposing or coexisting factor in a wide range of functional gastrointestinal disorders in infants and children. Pathogenesis of both conditions is complex and multiple mechanisms including dysmotility and hypersensitivity might contribute to the clinical manifestations. Data supporting the possible role of food allergies in the pathogenesis of FAPDs are limited. CMA may predispose to early life inflammation and visceral hypersensitivity, which in turn might manifest as FAPDs. The diagnosis of either CMA or FAPDs and distinction between them is challenging because of nonspecific and overlapping symptoms. Lack of accurate allergy tests in non-IgE (immunoglobulin E) mediated cases is also problematic. Oral food challenge, following an elimination diet, should be performed to diagnose a suspected non-IgE CMA allergy in children with FAPDs. In the management of FAPDs, an elimination diet should be considered for a limited period to verify if the symptoms improve or resolve.

Very early introduction of semisolid foods in preterm infants does not increase food allergies or atopic dermatitis

BACKGROUND

The optimal age for the introduction of solid foods for infants has long been a controversial issue.

OBJECTIVE

To determine whether the early introduction of semisolid foods influences the incidence of food allergy or atopic dermatitis among preterm infants.

METHODS

Retrospective data from 464 preterm infants born in Oulu University Hospital between 2008 and 2012 were analyzed. Age- and sex-matched full-term control children from the general population were identified. The primary outcome of the study was the difference in timing of the introduction of complementary feeding between preterm and full-term infants. The secondary outcomes were the incidences of food allergies and atopic dermatitis by the ages of 1 and 2 years.

RESULTS

Semisolid food was introduced at the median corrected age of 1.4 months for all preterm infants, at 1.9 months for late preterm, at 0.9 months for very preterm, and at 0.1 months for extremely preterm infants. The cumulative incidence, either of food allergies or of atopic dermatitis, did not differ significantly between preterm infants and controls by the ages of 1 and 2 years.

CONCLUSION

The very early introduction of complementary foods into the diet of preterm babies did not increase the incidence of food allergies or atopic dermatitis even among the most preterm infants. This finding supports the hypothesis that the gut-associated lymphoid tissue of preterm infants is ready to encounter food proteins and to begin the maturation process within 3 to 6 months of birth, regardless of gestational age.

Postnatal Innate Immune Development: From Birth to Adulthood

It is well established that adaptive immune responses are deficient in early life, contributing to increased mortality and morbidity. The developmental trajectories of different components of innate immunity are only recently being explored. Individual molecules, cells, or pathways of innate recognition and signaling, within different compartments/anatomical sites, demonstrate variable maturation patterns. Despite some discrepancies among published data, valuable information is emerging, showing that the developmental pattern of cytokine responses during early life is age and toll-like receptor specific, and may be modified by genetic and environmental factors. Interestingly, specific environmental exposures have been linked both to innate function modifications and the occurrence of chronic inflammatory disorders, such as respiratory allergies. As these conditions are on the rise, our knowledge on innate immune development and its modulating factors needs to be expanded. Improved understanding of the sequence of events associated with disease onset and persistence will lead toward meaningful interventions. This review describes the state-of-the-art on normal postnatal innate immune ontogeny and highlights research areas that are currently explored or should be further addressed.

Intestinal lesions are associated with altered intestinal microbiome and are more frequent in children and young adults with cystic fibrosis and cirrhosis

BACKGROUND AND AIMS

Cirrhosis (CIR) occurs in 5-7% of cystic fibrosis (CF) patients. We hypothesized that alterations in intestinal function in CF contribute to the development of CIR.

AIMS

Determine the frequency of macroscopic intestinal lesions, intestinal inflammation, intestinal permeability and characterize fecal microbiome in CF CIR subjects and CF subjects with no liver disease (CFnoLIV).

METHODS

11 subjects with CFCIR (6 M, 12.8 yrs ± 3.8) and 19 matched with CFnoLIV (10 M, 12.6 yrs ± 3.4) underwent small bowel capsule endoscopy, intestinal permeability testing by urinary lactulose: mannitol excretion ratio, fecal calprotectin determination and fecal microbiome characterization.

RESULTS

CFCIR and CFnoLIV did not differ in key demographics or CF complications. CFCIR had higher GGT (59±51 U/L vs 17±4 p = 0.02) and lower platelet count (187±126 vs 283±60 p = 0.04) and weight (-0.86 ± 1.0 vs 0.30 ± 0.9 p = 0.002) z scores. CFCIR had more severe intestinal mucosal lesions on capsule endoscopy (score ≥4, 4/11 vs 0/19 p = 0.01). Fecal calprotectin was similar between CFCIR and CFnoLIV (166 μg/g ±175 vs 136 ± 193 p = 0.58, nl <120). Lactulose:mannitol ratio was elevated in 27/28 subjects and was slightly lower in CFCIR vs CFnoLIV (0.08±0.02 vs 0.11±0.05, p = 0.04, nl ≤0.03). Small bowel transit time was longer in CFCIR vs CFnoLIV (195±42 min vs 167±68 p<0.001, nl 274 ± 41). Bacteroides were decreased in relative abundance in CFCIR and were associated with lower capsule endoscopy score whereas Clostridium were more abundant in CFCIR and associated with higher capsule endoscopy score.

CONCLUSIONS

CFCIR is associated with increased intestinal mucosal lesions, slower small bowel transit time and alterations in fecal microbiome. Abnormal intestinal permeability and elevated fecal calprotectin are common in all CF subjects. Disturbances in intestinal function in CF combined with changes in the microbiome may contribute to the development of hepatic fibrosis and intestinal lesions.

Prevention of infectious complications after heart surgery in children: procalcitonin-guided strategy

Introduction

Infectious complications remain a significant problem of modern cardiac surgery. New prevention strategies, based on the pathogenesis of such complications occurring after cardiopulmonary bypass (CPB) procedures, should be evaluated.

Aim of the study

To evaluate the effectiveness of a procalcitonin (PCT)-guided strategy involving the use of IgM-enriched intravenous immunoglobulins (IVIGs) in children with congenital heart disease with systemic inflammation during the early postoperative period.

Material and methods

Sixty consecutive patients aged 25 (21-30) months who underwent cardiac surgery with CPB and had blood PCT levels > 2 ng/mL on the 1^st postoperative day were enrolled in this single-center prospective randomized clinical trial. The patients were randomized into two groups, comparable in terms of the severity of their initial condition, age, and CPB time. IgM-enriched IVIGs (Pentaglobin, Biotest Pharma GmbH, Germany) were administered during the first 3 postoperative days (5 mL/kg each day) in the study group (n = 30) in addition to the standard treatment, which was also provided to the control group (n = 30). The data are presented as medians with 25-75^th percentiles; they were compared by the Mann-Whitney U-test, and p values of < 0.05 were considered as statistically significant.

Results

Postoperatively, 1/30 (3.3%) patients in the study group and 8/30 (26.7%) in the control group suffered from infectious complications (study group: urinary tract infection [UTI] – 1; control group: pneumonia – 4, pneumonia and sepsis – 2, peritonitis with multiorgan failure – 1, UTI – 1), p = 0.03. The length of hospital stay in the study group was shorter than in the control group: 19 (16-23) days vs. 24 (19-29) days, p = 0.002, as was the length of intensive care unit (ICU) stay: 3 (2-4) days vs. 4 (2-8) days, p = 0.03.

Conclusions

High PCT levels on the 1st postoperative day are associated with an increased risk of infectious complications after cardiac surgery. Early administration of IgM-enriched IVIGs can prevent the development of infectious complications.

Changes in intestinal glucocorticoid sensitivity in early life shape the risk of epithelial barrier defect in maternal-deprived rats

Glucocorticoids (GC) contribute to human intestine ontogeny and accelerate gut barrier development in preparation to birth. Rat gut is immature at birth, and high intestinal GC sensitivity during the first two weeks of life resembles that of premature infants. This makes suckling rats a model to investigate postpartum impact of maternal separation (MS)-associated GC release in preterm babies, and whether GC sensitivity may shape MS effects in immature gut. A 4 hours-MS applied once at postnatal day (PND)10 enhanced plasma corticosterone in male and female pups, increased by two times the total in vivo intestinal permeability (IP) to oral FITC-Dextran 4 kDa (FD4) immediately after the end of MS, and induced bacterial translocation (BT) to liver and spleen. Ussing chamber experiments demonstrated a 2-fold increase of permeability to FD4 in the colon immediately after the end of MS, but not in the ileum. Colonic permeability was not only increased for FD4 but also to intact horseradish peroxidase 44 kDa in MS pups. In vivo, the glucocorticoid receptor (GR) antagonist RU486 or ML7 blockade of myosin light chain kinase controlling epithelial cytoskeleton contraction prevented MS-induced IP increase to oral FD4 and BT. In addition, the GR agonist dexamethasone dose-dependently mimicked MS-increase of IP to oral FD4. In contrast, MS effects on IP to oral FD4 and BT were absent at PND20, a model for full-term infant, characterized by a marked drop of IP to FD4 in response to dexamethasone, and decreased GR expression in the colon only compared to PND10 pups. These results show that high intestinal GC responsiveness in a rat model of prematurity defines a vulnerable window for a post-delivery MS, evoking immediate disruption of epithelial integrity in the large intestine, and increasing susceptibility to macromolecule passage and bacteremia.

Intestinal permeability in normally nourished and malnourished children with and without diarrhea

We evaluated the association between diarrhea, malnutrition and intestinal function using the lactulose-mannitol test. Our study showed that a third of all children have abnormal intestinal permeability, there was an expected increase of permeability in children with acute diarrhea and alteration in intestinal permeability was greater in children with concurrent malnutrition and diarrhea.

Intestinal permeability in children with food allergy on specific elimination diets

BACKGROUND

Children with food allergy have been shown to have increased small intestinal permeability (IP) following ingestion of the offending food as well as during elimination diets. We investigated IP in asymptomatic food allergic children during an elimination diet to identify clinical characteristics associated with altered IP.

METHODS

Urinary recovery ratios of lactulose and mannitol (L/M) were determined 5 h following ingestion of 7.5 g of lactulose and 2 g of mannitol in 131 cow's milk and egg allergic children. An L/M ratio of ≥0.025 was considered abnormal based upon previously established laboratory internal references. A chart review was conducted to assess the clinical characteristics of these patients.

RESULTS

A total of 50 (38%) of the 131 children (median 6.7, range 4.8-8.9 yr; 66.2% male) with food allergy had elevated IP while asymptomatic on strict elimination diets. Age and height negatively correlated with IP. However, in the regression model analysis, abnormal IP was associated with shorter stature independently of age. Otherwise, food allergic patients with increased IP were comparable in gender, nutritional status, age of onset of food allergy, history of reactions, atopic diseases, and family history of food allergies to those with normal IP.

CONCLUSIONS

Elevated IP was found in about one-third of asymptomatic food allergic children on elimination diets and was associated with shorter stature. Our results suggest that increased IP may be an intrinsic trait in a subset of food allergic children. However, large, prospective studies are necessary to determine the role of impaired intestinal barrier in food allergy.

Nutrition in burns: Galveston contributions

Aggressive nutrition support is recommended following severe burn injury. Initially, such injury results in a prolonged and persistent hypermetabolic response mediated by a 10- to 20-fold elevation in plasma catecholamines, cortisol, and inflammatory mediators. This response leads to twice-normal metabolic rates, whole-body catabolism, muscle wasting, and severe cachexia. Thus, it is relevant to review the literature on nutrition in burns to adjust/update treatment. Failure to meet the increased substrate requirements may result in impaired wound healing, multiorgan dysfunction, increased susceptibility to infection, and death. Therefore, aggressive nutrition support is essential to ensure adequate burn care, attenuate the hypermetabolic response, optimize wound healing, minimize devastating catabolism, and reduce morbidity and mortality. Here, the authors provide nutrition recommendations gained from prospective trials, retrospective analyses, and expert opinions based on the authors' practices in Galveston, Texas, and Vienna, Austria.

What, how, and how much should patients with burns be fed?

The hypermetabolic response to severe burn injury is characterized by hyperdynamic circulation and profound metabolic, physiologic, catabolic, and immune system derangements. Failure to satisfy overwhelming energy and protein requirements after, and during, severe burn injury results in multiorgan dysfunction, increased susceptibility to infection, and death. Attenuation of the hypermetabolic response by various pharmacologic modalities is emerging as an essential component of the management of patients with severe burn injury. This review focuses on the more recent advances in therapeutic strategies to attenuate the hypermetabolic response and its postburn-associated insulin resistance.

The gut as communicator between environment and host: immunological consequences

During human evolution, the mucosal immune system developed two anti-inflammatory mechanisms: immune exclusion by secretory antibodies (SIgA and SIgM) to control epithelial colonization of microorganisms and inhibit penetration of harmful substances; and immunosuppression to counteract local and peripheral hypersensitivity against innocuous antigens such as food proteins. The latter function is referred to as oral tolerance when induced via the gut. Similar mechanisms also control immunity to commensal bacteria. The development of immune homeostasis depends on "windows of opportunity" where adaptive and innate immunities are coordinated by antigen-presenting cells; their function is not only influenced by microbial products but also by dietary constituents, including vitamin A and lipids like polyunsaturated omega-3 fatty acids. These factors can in several ways exert beneficial effects on the immunophenotype of the infant. Also breast milk provides immune-modulating factors and SIgA antibodies - reinforcing the gut barrier. Mucosal immunity is most abundantly expressed in the gut, and the intestinal mucosa of an adult contains at least 80% of the body's activated B cells - terminally differentiated to plasmablasts and plasma cells (PCs). Most mucosal PCs produce dimeric IgA which is exported by secretory epithelia expressing the polymeric Ig receptor (pIgR), also called membrane secretory component (SC). Immune exclusion is therefore performed mainly by SIgA. Notably, pIgR knockout mice which lack SIgs show increased uptake of food and microbial antigens and they have a hyper-reactive immune system with disposition for anaphylaxis; but this untoward development is counteracted by cognate oral tolerance induction as a homeostatic back-up mechanism.

Update on mucosal immunoglobulin A in gastrointestinal disease

PURPOSE OF REVIEW

To review recent findings dealing with the involvement of mucosal immunoglobulin A (IgA) in the gut barrier function and various gastrointestinal diseases. New information will be discussed in the context of previous knowledge in this field.

RECENT FINDINGS

The epithelial barrier function seems to be central in many mucosal disorders because it is decisive for host-microbial interactions and penetration of soluble antigens into the lamina propria. Secretory IgA contributes to the barrier function and recent evidence strongly supports the notion that such antibodies are involved in immunological homeostasis.

SUMMARY

Inflammatory bowel disease involves a break of tolerance to the commensal microbiota. Aberrations in the mucosal IgA system may, therefore, be part of the inflammatory bowel disease pathogenesis. In gluten-induced enteropathy, however, it has been suggested that a mucosal IgA response may promote the progression of celiac disease and dermatitis herpetiformis by enhancing the uptake of gluten peptides and inhibiting the enzyme activity of tissue transglutaminase. A mucosal IgA response may also promote gastritis by protecting Helicobacter pylori from complement attack. In food allergy, several facets of the epithelial barrier function may show deficiency, including secretory IgA.

Food allergy: separating the science from the mythology

Numerous genes are involved in innate and adaptive immunity and these have been modified over millions of years. During this evolution, the mucosal immune system has developed two anti-inflammatory strategies: immune exclusion by the use of secretory antibodies to control epithelial colonization of microorganisms and to inhibit the penetration of potentially harmful agents; and immunosuppression to counteract local and peripheral hypersensitivity against innocuous antigens, such as food proteins. The latter strategy is called oral tolerance when induced via the gut. Homeostatic mechanisms also dampen immune responses to commensal bacteria. The mucosal epithelial barrier and immunoregulatory network are poorly developed in newborns. The perinatal period is, therefore, critical with regard to the induction of food allergy. The development of immune homeostasis depends on windows of opportunity during which innate and adaptive immunity are coordinated by antigen-presenting cells. The function of these cells is not only orchestrated by microbial products but also by dietary constituents, including vitamin A and lipids, such as polyunsaturated omega-3 fatty acids. These factors may in various ways exert beneficial effects on the immunophenotype of the infant. The same is true for breast milk, which provides immune-inducing factors and secretory immunoglobulin A, which reinforces the gut epithelial barrier. It is not easy to dissect the immunoregulatory network and identify variables that lead to food allergy. This Review discusses efforts to this end and outlines the scientific basis for future food allergy prevention.

Non-invasive assessment of barrier integrity and function of the human gut

Over the past decades evidence has been accumulating that intestinal barrier integrity loss plays a key role in the development and perpetuation of a variety of disease states including inflammatory bowel disease and celiac disease, and is a key player in the onset of sepsis and multiple organ failure in situations of intestinal hypoperfusion, including trauma and major surgery. Insight into gut barrier integrity and function loss is important to improve our knowledge on disease etiology and pathophysiology and contributes to early detection and/or secondary prevention of disease. A variety of tests have been developed to assess intestinal epithelial cell damage, intestinal tight junction status and consequences of intestinal barrier integrity loss, i.e. increased intestinal permeability. This review discusses currently available methods for evaluating loss of human intestinal barrier integrity and function.

Induction of secretory immunity and memory at mucosal surfaces

Mucosal epithelia comprise an extensive vulnerable barrier which is reinforced by numerous innate defence mechanisms cooperating intimately with adaptive immunity. Local generation of secretory IgA (SIgA) constitutes the largest humoral immune system of the body. Secretory antibodies function both by performing antigen exclusion at mucosal surfaces and by virus and endotoxin neutralization within epithelial cells without causing tissue damage. SIgA is thus persistently containing commensal bacteria outside the epithelial barrier but can also target invasion of pathogens and penetration of harmful antigens. Resistance to toxin-producing bacteria such as Vibrio cholerae and enterotoxigenic Escherichia coli appears to depend largely on SIgA, and so does herd protection against horizontal faecal-oral spread of enteric pathogens under naïve or immunized conditions--with a substantial innate impact both on cross-reactivity and memory. Like natural infections, live mucosal vaccines or adequate combinations of non-replicating vaccines and mucosal adjuvants, give rise not only to SIgA antibodies but also to longstanding serum IgG and IgA responses. However, there is considerably disparity with regard to migration of memory/effector cells from mucosal inductive sites to secretory effector sites and systemic immune organs. Also, although immunological memory is generated after mucosal priming, this may be masked by a self-limiting response protecting the inductive lymphoid tissue in the gut. The intranasal route of vaccine application targeting nasopharynx-associated lymphoid tissue may be more advantageous for certain infections, but only if successful stimulation is achieved without the use of toxic adjuvants that might reach the central nervous system. The degree of protection obtained after mucosal vaccination ranges from reduction of symptoms to complete inhibition of re-infection. In this scenario, it is often difficult to determine the relative importance of SIgA versus serum antibodies, but infection models in knockout mice strongly support the notion that SIgA exerts a decisive role in protection and cross-protection against a variety of infectious agents. Nevertheless, relatively few mucosal vaccines have been approved for human use, and more basic work is needed in vaccine and adjuvant design, including particulate or live-vectored combinations.

Enteral resuscitation and early enteral feeding in children with major burns--effect on McFarlane response to stress

AIM

Early enteral feeding has become standard practice for burned patients. The aim of this study was to determine whether early enteral feeding could be used as an avenue for resuscitation and feeding and the effect it would have on the induction/amelioration of the hormonal stress response.

METHOD

Eighteen children with <20% TBSA were randomly assigned to either early enteral feeding and resuscitation, or intravenous resuscitation with the induction of enteral feeding delayed. The enteral fluid volume was incrementally increased every 3h with a simultaneous equal reduction in the intravenous volume until all the calculated intravenous fluid requirements for resuscitation and maintenance could be administered enterally. In the second group, intravenous resuscitation continued for 48 h when enteral feeding was introduced. Parameters measured were the clinical responses and outcome as well as the concentrations of insulin, insulin-like growth factor 1, glucagon, cortisone and growth hormone. The estimated and calculated energy expenditure was measured calorimetrically and bowel permeability was assessed using a dual sugar absorption test.

RESULTS

Three children were excluded from the study because of early death from organ failure or carbon monoxide poisoning. Early enteral resuscitation and feeding (ER/EEF) was initiated within a median of 10.7h post-burn in nine children and late enteral feeding introduced on an average 54 h post-burn. The ER/EEF group showed an anabolic response with significantly higher insulin concentrations (p=0.008) and insulin: glucagon ratios (p=0.043). Although blood glucose concentrations were initially slightly elevated (EEF: 10.3g/l, LEF: 8.1g/l), they rapidly returned to within the normal range. The cortisol and IGF1 concentrations did not differ significantly between the two treatment groups. Growth hormone concentrations were significantly higher in the late enteral feeding (LEF) group (p=0.03). The estimated energy expenditure was not different amongst the groups. Small bowel permeability [lactulose:rhamnose (L:R) ratios] decreased significantly over time (p=0.02) in both study groups. No pulmonary aspiration was found. Diarrhoea in the ER/EEF settled quickly (2-4 days), whereas in the LEF group it persisted for longer than a week. The LEF group lost a median of 7.75% (acceptable range=<or=5%) of admission body weight, whereas the ER/EEF group lost a median of 3.01%. Patients in the LEF group required antibiotic treatment for a longer period (p=0.08) and their hospital stay was longer, though not significant.

CONCLUSIONS

Enteral resuscitation and early enteral feeding is a safe and effective method and particularly suited for children in developing countries. It resulted in the amelioration of the hormonal stress response and improved outcome. Enteral resuscitation should not be introduced in a patient in shock or with existing gastrointestinal disease. Complications were minimal.

Effect of hyperbilirubinemia on intestinal permeability in healthy term newborns

We investigated the effect of serum bilirubin (SB) on intestinal permeability (IP) of healthy, term, birth weight appropriate for gestational age neonates before phototherapy. IP was measured by the dual probe (lactulose/mannitol) sugar absorption test (SAT) performed on the third day of life in 12 healthy jaundiced newborns (total bilirubin 249 +/- 39.75 micromol/L) and compared to that of 12 non-jaundiced newborns (total bilirubin 83.79 + 37.62 micromol/L) matched for sex, gestational age, birth weight and Apgar score. Jaundiced newborns have a significantly higher La/Ma ratio than non-jaundiced (0.31 +/- 0.28 vs. 0.053 +/- 0.043; p < 0.0004). A significant correlation was found between serum bilirubin level and La/Ma ratio (r = 0.56 p < 0.006).

CONCLUSION

Our study demonstrates a direct effect of UCB on gut epithelial barrier of at-term newborns in whom UCB appears to be responsible for an alteration of IP that theoretically may lead to a passage of macromolecules through the intestinal epithelium increasing the risk of sensitization.

Gut barrier dysfunction in food allergy

Intestinal permeability tests used in the diagnosis of allergic diseases in response to oral food challenge have led to the conclusion that constitutive defects of the intestinal barrier are not the primary cause of allergic diseases. However, perturbation of environmental factors (infection, stress), by increasing intestinal permeability and enhancing danger signals, may favour food allergy in susceptible individuals. The mechanisms of enhanced permeability to specific and bystander antigens have been delineated as well as the molecular events involved in the sequential phases of allergic reactions. Intestinal absorption of food antigens and immune responses are mutually dependent, and luminal (environmental) and serosal (intrinsic) factors synergize to maintain a self-perpetuating cycle in which antigens penetrate the mucosa and induce allergic inflammation.

Intestinal permeability in long-term follow-up of patients with celiac disease on a gluten-free diet

Intestinal permeability is frequently abnormal in patients with celiac disease. The long-term effect of a gluten-free diet on intestinal permeability and the correlation of intestinal permeability with a gluten-free diet are not known. The objectives of this study were to determine the responses of intestinal permeability and antibody testing to gluten free diet and the degree of correlation of these measurements with gluten ingestion. In this prospective study, patients with celiac disease were divided into three groups based on length of time on a gluten-free diet: Group A, < 1 month; Group B, 1 month-1 year; Group C, > 1 year. Patients in Groups B and C were tested at baseline and at 4-12 weeks later for the following: lactulose/mannitol intestinal permeability, endomysial antibody, and 3-day food record. Permeability tests were also performed in Group A and control subjects. Intestinal permeability was elevated in newly diagnosed celiac disease and in individuals on a gluten-free diet for less than 1 year. Intestinal permeability was normal in 80% at visit 1 and 87% at visit 2 in individuals with celiac disease on a gluten-free diet for more than a year. Trace gluten ingestion was associated with increased intestinal permeability on visit 2 (P = 0.0480). The sensitivity of detecting gluten ingestion as measured by a 3-day food record was higher for permeability testing (29 and 36%) compared with endomysial antibody testing (18 and 18%) for visits 1 and 2, respectively. Intestinal permeability normalizes in the majority of individuals with celiac disease on a gluten-free diet. Gluten ingestion as measured by a 3-day food record correlates with intestinal permeability measurements. The role of permeability testing in the follow-up of patients with celiac disease warrants further investigation.

Gut permeability in paediatric cardiac surgery

BACKGROUND

Intestinal mucosal ischaemia can occur in infants and children during and after cardiac surgery. Severe decreases in mucosal perfusion may cause complications such as necrotizing enterocolitis and postoperative mortality. We investigated gut permeability in paediatric patients undergoing cardiac surgery using the dual sugar permeability test and absorption of two other saccharides.

METHODS

Thirty-four patients undergoing palliative or corrective surgical procedures with and without cardiopulmonary bypass were investigated. Intestinal permeability was measured using 3-O-methyl-D-glucose, D-xylose, L-rhamnose and lactulose, given orally after induction of anaesthesia and 12 and 24 h later.

RESULTS

Lactulose/rhamnose ratios were raised from the outset [median 0.39 (confidence interval 0.07-1.8 for patients undergoing operations without cardiopulmonary bypass and 0.30 (0.02-2.6) with cardiopulmonary bypass]. The highest lactulose/rhamnose ratios were recorded 12 h after surgery 0.32 (0.07-6.9), when cardiopulmonary bypass was used. This is approximately seven times the value expected in healthy children. There was an improvement in patients not undergoing cardiopulmonary bypass: 0.22 (0.03-0.85) 12 h and 0.11 (0-0.48) 24 h after induction of anaesthesia. Patients undergoing repair of aortic coarctation showed the fastest recovery: 0.09 (0.03-0.31) 12 h and 0.07 (0.04-0.35) 24 h after induction of anaesthesia.

CONCLUSIONS

Patients with congenital heart defects have abnormal gut permeability when compared with healthy children of similar age. Cardiopulmonary bypass seems to affect the intestinal barrier morphologically (lactulose and rhamnose absorption) and functionally (3-O-methyl-D-glucose and D-xylose absorption).

Role of secretory antibodies in the defence against infections

Adaptive immunity mediated by secretory antibodies is important in the defence against mucosal infections. Specific secretory immunoglobulin A (SIgA) can inhibit initial pathogen colonization by performing immune exclusion both on the mucosal surface and within virus-infected secretory epithelial cells without causing tissue damage. Resistance against toxin-producing bacteria such as Vibrio cholerae appears to be particularly dependent on SIgA antibodies. Like natural infections, live topical vaccines or adequate combinations of inactivated vaccines and mucosal adjuvants give rise not only to SIgA antibodies, but also to long-standing serum IgG and IgA responses. The intranasal route of vaccine application could be particularly attractive to achieve this result, but only if successful stimulation is obtained without the use of toxic adjuvants. The degree of protection after vaccination may range from complete inhibition of reinfection to reduction of symptoms. In this scenario it is generally difficult to determine unequivocally the relative importance of SIgA versus serum antibodies. However, infection models in knockout mice strongly support the notion that SIgA exerts a decisive role in protection and cross-protection against a variety of infectious agents.

Regulation of the intestinal glycoprotein glycosylation during postnatal development: role of hormonal and nutritional factors

This review focuses on the regulation of the glycoprotein glycosylation process in small intestine and colon during postnatal development. Glycoproteins play a prominent part in intestine as mucins secreted by the goblet cells and as molecules of biological interest largely present in the microvillus membrane of the enterocytes (digestive enzymes, transporters). The age-related changes in the intestinal glycosylation control the quality of glycan chains of glycoproteins. Postnatal maturation is observed at all stages of the glycoprotein glycosylation. But it is essentially characterised in the external glycosylation by a shift from sialylation to fucosylation depending on the transcriptional regulation of the corresponding glycosyltransferases, but also on coordinate changes in the activities of glycosyltransferases and of their regulatory proteins, in nucleotide-sugar bioavailability and in product degradation by oxidases. Many factors have been evoked to trigger these changes, among which are hormonal (glucocorticoids, insulin) and dietary factors. Changes in the structure of the glycoprotein glycans might be important for the transport, the barrier function, the implantation of the immune defences and of the microflora and even probably for the biological activity of some digestive enzymes.

Use of an isolated intestinal circuit to evaluate the effect of ischemia and reperfusion on mucosal permeability of the equine jejunum

OBJECTIVES

To evaluate the efficacy of an isolated perfusion circuit and the effect of ischemia-reperfusion on mucosal permeability of the jejunum.

STUDY DESIGN

In vitro study of intestinal mucosal permeability.

ANIMALS

Twelve healthy adult horses.

METHODS

A control segment of jejunum was placed in an isolated perfusion circuit for 240 minutes and mucosal permeability was measured. After detecting no deleterious effects of the isolated system on the control intestine, low flow ischemia was created in experimental segments for 20, 40, 60 and 90 minutes followed by 60 minutes of reperfusion and mucosal permeability was evaluated. At the completion of the studies, histologic evaluation was used to determine mucosal grades, surface area, and volume.

RESULTS

Control tissue was maintained in the isolated circuit for 240 minutes without effect on mucosal grade, surface area, or volume relative to intact tissue. After ischemia-reperfusion, mucosal grade increased, and volume and surface area decreased progressively with longer periods of ischemia. Mucosal clearance of albumin remained constant during 240 minutes of perfusion in control tissue and was elevated after ischemia-reperfusion.

CONCLUSIONS

No deleterious changes were noted in jejunum perfused with this isolated circuit, whereas alterations in mucosal permeability were present after ischemia-reperfusion.

CLINICAL RELEVANCE

The isolated perfusion circuit successfully maintained an isolated segment of jejunum within physiologic limits, and can be used to evaluate the effects of injury and the efficacy of pharmaceuticals to attenuate these changes.

Experimentally induced gluten enteropathy and protective effect of epidermal growth factor in artificially fed neonatal rats

BACKGROUND

A protective effect of breast-feeding against the development of celiac disease has been described, but the nature and effects of the actual milk components have not been established. Epidermal growth factor (EGF), a milk cytokine affecting the proliferation and differentiation of mucosal epithelial cells, was studied as to its potential protective effect on the damage of intestinal mucosa by gliadin in a model system.

METHODS

Enteropathy was induced by gliadin in inbred AVN strain rat pups delivered by cesarean section, breast-fed, or hand-fed a milk formula. All experimental groups were treated with interferon-gamma (1,000 U per animal, administered intraperitoneally) after birth. Gliadin (0.5 and 3 mg) was intragastrically administered to the pups on days 0 and 3, and a 30-mg challenge dose was given on day 20 (24 hours before the termination of the experiment). One group of artificially fed pups received EGF (100 ng/ml) continuously in the diet.

RESULTS

Gliadin- and interferon-gamma-treated formula-fed rat pups showed villus atrophy, increase of inflammatory cells, including CD4+ T lymphocytes in the lamina propria, and damage to epithelial tight junctions and the enterocyte brush border. Morphometrically, the villus height was significantly less than in other groups. Recombinant EGF was markedly increased in the epithelial cells of injured jejunum. The intestinal mucosa of gliadin- and interferon-gamma-treated pups kept on a EGF-supplemented artificial diet resembled that of breast-fed pups.

CONCLUSION

Pathologic changes in jejunal mucosa (villus atrophy and inflammation) resembling gliadin-induced atrophy appeared on administration of interferon-gamma and gliadin to rat pups fed an artificial milk diet immediately after birth. Addition of EGF to the diet protected the rats against pathologic mucosal changes.

Gastroesophageal reflux and cow milk allergy: is there a link?

Gastroesophageal reflux (GER) and cow milk allergy (CMA) occur frequently in infants younger than 1 year. In recent years, the relation between these 2 entities has been investigated and some important conclusions have been reached: in up to half of the cases of GER in infants younger than 1 year, there may be an association with CMA. In a high proportion of cases, GER is not only CMA associated but also CMA induced. The frequency of this association should induce pediatricians to screen for possible concomitant CMA in all infants who have GER and are younger than 1 year. With the exception of some patients with mild typical CMA manifestations (diarrhea, dermatitis, or rhinitis), the symptoms of GER associated with CMA are the same as those observed in primary GER. Immunologic tests and esophageal pH monitoring (with a typical pH pattern characterized by a progressive, slow decrease in esophageal pH between feedings) may be helpful if an association between GER and CMA is suspected, although the clinical response to an elimination diet and challenge is the only clue to the diagnosis. This article reviews the main features of GER and CMA, focusing on the aspects in common and the discrepancies between both conditions.

Mucosal inflammation in a genetic model of spontaneous type I diabetes mellitus

The BioBreeding (BB) rat provides a model of spontaneous type I diabetes mellitus that closely resembles the human disease. Diabetes-prone BB rats demonstrate increased intestinal permeability prior to the development of insulinitis. Studies suggest that alterations in intestinal permeability can lead to increased intestinal inflammatory activity. Diabetes-prone (BBdp) and diabetes-resistant (BBdr) BB rats were examined at 45 days and at >70 days of age following the development of clinical disease (BBd). In separate experiments, tissue was assayed for myeloperoxidase (MPO) or fixed for histological assessment and immunohistochemistry. Blood was obtained for leukocyte MPO measurements and morphological assessment of circulating leukocytes. MPO activity was significantly elevated in the distal small intestine of 45-day-old BBdp rats. In contrast, at >70 days of age, MPO activity was significantly increased throughout the small intestine of BBd and non-diabetic BBdp rats. Subsequently, all measurements were performed in >70-day-old rats. An increase in inflammatory infiltrate was noted in the distal small intestine of BBd rats by light microscopy. Infiltrating cells were identified as bands (a maturing cell type of the neutrophil lineage) and mature neutrophils. The findings suggest diabetes susceptibility is associated with an increase in intestinal inflammatory activity.

Influence of age and body size on intestinal permeability and absorption in healthy dogs

OBJECTIVE

To evaluate effects of age and body size of dogs on intestinal permeability (unmediated diffusion) as measured by the ratio of urinary lactulose to L-rhamnose (L:R) and absorption (carrier-mediated transport) as measured by the ratio of urinary D-xylose to 3-O-methyl-D-glucose (X:MG) and to determine whether these variables correlated with fecal quality.

ANIMALS

6 Miniature Poodles, 6 Standard Schnauzers, 6 Giant Schnauzers, and 6 Great Danes.

PROCEDURE

A solution that contained lactulose and rhamnose or xylose and 3-O-methyl-D-glucose was administered orally to dogs that were 12, 22, 36, and 60 weeks old. Urine was collected 6 hours later, and urinary L:R and X:MG were calculated. Fecal moisture and scoring were recorded during the same periods.

RESULTS

Age and breed did not affect intestinal absorption, and we did not detect a relationship between X:MG and fecal variables. In contrast, we detected significant effects of age and body size on intestinal permeability. Puppies (12 weeks old) and large dogs had higher intestinal permeability than adult (60 weeks old) and small dogs. The increased intestinal permeability in large dogs was associated with lower fecal quality as indicated by the significant positive correlations between L:R and fecal moisture (r, 0.61) and L:R and fecal scores (r, 0.86) in adult dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

These results indicate that age and body size should be considered when assessing intestinal permeability by use of the L:R urinary excretion test in dogs. High intestinal permeability could be a possible cause of poor fecal quality in large dogs.

Polyamine participation in the maturation of glycoprotein fucosylation, but not sialylation, in rat small intestine

The aim of this study was to determine the role of polyamines in the diet-related maturation of the intestinal glycoprotein glycosylation during postnatal development in the rat. The activity of alpha-2,6-sialyltransferase and the sialylated forms of glycoproteins in the intestinal brush-border membranes were found to decrease considerably after weaning, in parallel with the intestinal level of putrescine. By contrast, the activity of alpha-1,2-fucosyltransferases, the mRNA levels for two alpha-1,2-fucosyltransferase genes, FTA and FTB, and the fucosylated forms of glycoproteins all increased after weaning, in parallel with the levels of spermidine and spermine. These results suggest a possible role of polyamines in the evolution of glycosylation. The treatment of suckling rats with spermidine or spermine reproduced the high intestinal levels of these polyamines corresponding to those normally found after weaning. After these treatments, a rise in the activity of the alpha-1,2-fucosyltransferase was observed, associated with a fall in alpha-L-fucosidase activity. The alpha-1,2-fucosyltransferase FTB gene was found to be regulated at the transcriptional level, but not by its inhibitor, fuctinin. The result of these variations was the precocious appearance of several alpha-1,2-fucoproteins, which are normally found in brush-border membranes after weaning. The treatment of suckling rats with putrescine, which induced only a transitory rise in intestinal putrescine, had a similar but weaker effect on the fucosylation process than spermidine or spermine, and treatment with ornithine was ineffective. alpha-2,6-Sialylation was not affected by any of the treatments. Spermidine and spermine turned out to be more effective than putrescine for intestinal glycoprotein fucosylation, but did not affect their sialylation. Spermidine and spermine, whose intestinal levels where found to increase at weaning time, may have been partly responsible for the natural evolution of the intestinal glycoprotein fucosylation that occurred during this period.

Sensitivity of a hyperosmolar or "low"-osmolar test solution for sugar absorption in recognizing small intestinal mucosal damage in coeliac disease

Reliability of differential sugar absorption tests is hampered by a lack of standardization of the content and osmolarity of the test solutions. We evaluated the effect of osmolarity of the test solution of the sugar absorption test on the 5 hour urine excretion of orally administered lactulose and mannitol. A group of 28 controls and 14 coeliacs, with villous atrophy grade II to IV, ingested a hyperosmolar sugar absorption test solution and a "low"-osmolar solution, respectively. After an overnight fast, each subject ingested hyperosmolar sugar absorption test solution (2 g mannitol, 5 g lactulose and 40 g sucrose/100 ml (around 1,560 mmol/l)). After two days, this procedure was repeated with low-osmolar solution (2 g mannitol and 5 g lactulose/100 ml (around 375 mmol/l). The influence of the sequence of the tests on the results had previously been excluded. All urine from the 5 h-period following ingestion of the test solution was collected. To calculate the low-osmolar solution ratio, samples were analysed for lactulose and mannitol concentrations by gas chromatography The sensitivity of hyperosmolar SAT solution and low-osmolar solution for the detection of mucosal abnormalities in coeliacs was 64% and 43%, respectively. In conclusion, a hyperosmolar solution discriminates better between normal and damaged mucosa of the small bowel such as villous atrophy due to a relative increase in permeability for lactulose.

Dual sugar permeability testing in diarrheal disease

OBJECTIVE

To assess the validity of the use of a blood specimen for the sugar permeability test because of the high failure rate of 5-hour urine collection in young children with diarrhea.

STUDY DESIGN

Simultaneous 5-hour urine collections and timed blood tests were taken after ingestion of an isotonic solution of lactulose (L) and L-rhamnose (R) in 24 children with acute gastroenteritis and 25 children without diarrhea in a control group. Sugars were measured with high performance liquid chromatography, and the percent of recovered sugars was expressed as an L-R ratio.

RESULTS

With acute gastroenteritis the geometric mean L-R ratios (95% confidence intervals) were 12.4 (9.3 to 16.3) in urine and 9.4 (6.7 to 13.1) in blood compared with 6.7 (5.0 to 8.8) and 5.9 (4.4 to 7.8), respectively, in the control group. The level of agreement (kappa) among normal, intermediate, and high ratios for blood and urine was 0.71 (0.51 to 0.92). The failure rate of L-R tests was significantly reduced with a blood specimen (urine 37% vs blood 10%; P <.0001).

CONCLUSIONS

Intestinal permeability testing on a blood specimen is a valid alternative to urine collection in young children and has a significantly lower test failure rate.

Enhanced peptide-binding capacities of small intestinal brush border membranes in celiac disease

In pathogenesis of celiac disease, the significance of prolamin peptide interactions with enterocytes is controversial. Changes in cellular metabolism induced by gliadin peptides, as well as uptake and presentation by enterocytes, are discussed. We analyzed peptide binding to enterocytic membranes as a potential key event. Binding capacities of brush border membranes isolated from small intestinal biopsies of untreated (n = 49) and treated celiac patients on a gluten-free diet (n = 30), as well as control subjects (n = 43), were measured with a dot blot chemiluminescence assay. Synthetic gliadin peptides comprising amino acid position 8-19 (G XIV) and 30-41 (G XI) of alpha-gliadins, a peptic-tryptic digest of gliadin (PT-GLI), and a synthetic zein peptide were used. Comparing treated celiac patients with controls, we observed significantly enhanced membrane-binding of PT-GLI [mean 122.4 densitometric units/microg (95% confidence interval 116.0-128.9) vs 108.9 (102.1-115.7)] and of zein peptide [50.2 (38.4-61.9) vs 28.8 (13.4-44.2)], but only slightly increased binding of the synthetic gliadin peptides G XIV [65.5 (60.6-70.5) vs 62.4 (56.3-68.5) and G XI [75.2 (69.8-80.6) vs 65.9 (55.2-76.5)]. Independent of patient group, membrane-binding capacities for celiac-active gliadin peptides exceeded those of the zein peptide. Thus, interaction of gliadin peptides with the apical enterocytic membrane was not found exclusively in celiac disease. Furthermore, increased binding capacities in treated celiac disease were not confined to celiac-active peptides. Quantitative differences in gliadin peptide binding as a primary characteristic in celiac disease might contribute to pathogenetic effects exerted on small intestinal epithelial cells.

Sucrose permeability as a means of detecting diseases of the upper digestive tract

The healthy gastric epithelium will not allow easy permeation of a disaccharide-sized molecule such as sucrose. However, during gastric damage, intact sucrose can pass the gastric epithelium and ultimately appear in the urine. We examined the relationship between total urinary sucrose excretion and various diseases. We used 149 patients (105 had upper gastrointestinal disease, 12 had gastric cancer and 32 were normal). Subjects were given a solution containing 100 g sucrose in 450 c.c. water. All urine was collected for 7.5 h. The urinary sucrose concentration was determined by anion exchange high-performance liquid chromatography. Total urinary sucrose excretion was significantly higher in patients with gastric ulcer and those with gastric cancer than in endoscopically normal controls. In the 34 patients with gastric ulcer, the total sucrose excretion was closely correlated with ulcer size. Ulcer location did not affect urinary sucrose excretion. A strong correlation was also observed between sucrose excretion and lesion size in the 12 patients with gastric cancer. The sucrose permeability test may be a relatively sensitive method to detect gastric disease.

Simultaneous HPLC determination with light-scattering detection of lactulose and mannitol in studies of intestinal permeability in pediatrics

We describe a new HPLC method for the simultaneous determination of lactulose and mannitol in urine, in which cation-exchange chromatography and evaporative light-scattering detection are used. The two sugars are orally administered for the estimation of intestinal permeability in children. Samples were purified by solid phase extraction on a C18 cartridge and subsequent addition of anion-exchange resin. Cellobiose may be used as an internal standard. The chromatographic separation was carried out in 16 min at a flow rate of 0.5 mL/min, using deionized water as the mobile phase. Within-run precision (CV) measured at three concentrations was 1.6–2.3% for lactulose and 1.0–1.9% for mannitol. Between-run CVs were 2.1–4.1% and 1.3–2.7% for lactulose and mannitol, respectively. Analytical recovery of both sugar probes was 97–101%. The detection limits (signal-to-noise ratio = 3) were 0.82 mg/L for lactulose and 0.65 mg/L for mannitol. The lactulose/mannitol ratio in control subjects was 0.024 ± 0.006; in patients with Crohn’s and coeliac diseases in active phase, the ratios were 0.200 ± 0.082 and 0.072 ± 0.025, respectively. The method is rapid, simple, and sensitive, and suitable for determination of intestinal permeability in children.

Is there IgA from gut mucosal origin in the serum of children with Henoch-Schönlein purpura?

Thirty-two children with Henoch-Schönlein purpura with or without renal symptoms were studied to characterize the IgA hyperglobulinemia observed in the serum of most patients. It was shown that only the IgA1 subclass concentration was increased. Secretory IgA and IgA to gliadin levels were frequently increased in serum, with a good correlation between them. Circulating IgA immune complexes were detected often and contained high activity to gliadin. In contrast, IgA activity to tetanus toxoid did not change. We failed to show any differences in renal involvement. These data suggest that elevation of serum IgA in Henoch-Schönlein purpura is due in part to a disturbance of the gut mucosal immune system, and the presence of circulating IgA immune complexes with dietary antigens can be postulated but cannot explain the occurrence of urinary symptoms.

Introduction of enteral feeding in neonates on extracorporeal membrane oxygenation after evaluation of intestinal permeability changes

BACKGROUND/PURPOSE

Neonates meeting criteria for extracorporeal membrane oxygenation (ECMO) often suffer from variable periods of hypoxia. During ECMO, starvation of the gut is common practice in many centres as splanchnic ischemia results in loss of intestinal integrity, which in turn predisposes for bacterial translocation and sepsis and eventually necrotizing enterocolitis (NEC) and multiorgan failure. However, minimal enteral feeding is thought to be of benefit in the critically ill. Data on intestinal integrity in newborns on ECMO and the effects of enteral nutrition are not available. This study prospectively evaluates the changes in small intestinal integrity in 16 neonatal ECMO patients.

METHODS

With 2-day intervals, excretion percentages of lactulose/L-rhamnose (nonmediated diffusion), D-xylose (passive), and 3-O-methyl-D-glucose (active carrier-mediated transport) were measured by gas-liquid chromatography in a 4-hour urine sample. After obtaining baseline data in nine patients, enteral feeding was started in the next seven patients between the third and the ninth day of ECMO.

RESULTS

Thirteen patients had increased lactulose/L-rhamnose ratios (>0.05) consistent with increased intestinal permeability. In three patients the lactulose/L-rhamnose ratios were within the normal range. D-xylose excretion percentages were normal (or slightly increased) in 11 patients consistent with normal (or increased) passive carrier-mediated transport. 3-O-methyl-D-glucose excretion percentages were decreased (<10%) in all but one patient, consistent with decreased active carrier-mediated transport. After introduction of enteral nutrition no significant changes of these parameters were seen.

CONCLUSIONS

The authors conclude that intestinal integrity is compromised in neonates on ECMO and that introduction of enteral nutrition does not result in further deterioration. This conclusion does not support the practice of withholding enteral nutrition in critically ill newborns supported by ECMO.

Intestinal permeability in kwashiorkor

Intestinal permeability can be assessed non-invasively using the lactulose-rhamnose (L-R) test, which is a reliable measure of small intestinal integrity.

AIMS

To determine risk factors for abnormal intestinal permeability in kwashiorkor, and to measure changes in L-R ratios with inpatient rehabilitation.

DESIGN

A case-control study of 149 kwashiorkor cases and 45 hospital controls. The L-R test was adapted to study kwashiorkor in Malawi, with testing at weekly intervals during nutritional rehabilitation. Urine sugars were measured by thin layer chromatography in London.

RESULTS

The initial geometric mean L-R ratios (x100) (with 95% confidence interval) in kwashiorkor were 17.3 (15.0 to 19.8) compared with 7.0 (5.6 to 8.7) for controls. Normal ratios are < 5, so the high ratios in controls indicate tropical enteropathy syndrome. Abnormal permeability in kwashiorkor was associated with death, oliguria, sepsis, diarrhoea, wasting and young age. Diarrhoea and death were associated with both decreased L-rhamnose absorption (diminished absorptive surface area) and increased lactulose permeation (impaired barrier function) whereas nutritional wasting affected only L-rhamnose absorption. Despite, clinical recovery, mean L-R ratios improved little on treatment, with mean weekly ratios of 16.3 (14.0 to 19.0), 13.3 (11.1 to 15.9) and 14.4 (11.0 to 18.8).

CONCLUSION

Abnormal intestinal permeability in kwashiorkor correlates with disease severity, and improves only slowly with nutritional rehabilitation.

Effect of intestinal helminthiasis on intestinal permeability of early primary schoolchildren

Intestinal permeability of 246 early primary schoolchildren at 2 schools (106 of whom were infected with intestinal helminths) was assessed by using the lactulose/mannitol differential absorption test. The ratio of the urinary recoveries of lactulose and mannitol was determined after oral administration of a standard solution of the 2 sugars. Assessment of intestinal permeability was repeated on 100 infected children after treatment and on a cohort of 68 uninfected children. Infected and uninfected groups were compared with respect to baseline lactulose/mannitol ratio (L/M1) and change in lactulose/mannitol ratio between assessments (delta L/M). The correlations between baseline intensity of infection and L/M1, and between fall in intensity and delta L/M, were evaluated. Based on a crude index of socioeconomic status, each child was assigned to one of 3 socioeconomic groups; all but 3 children belonged to either groups 2 or 3. Trichuris trichiura and Ascaris lumbricoides were the 2 predominant infections; the hookworm infection rate was relatively low. The results suggested that helminthiasis exerted only a marginal effect on intestinal permeability, the impact of which in children from lower socioeconomic backgrounds was negligible in comparison with the cumulative effects of other factors.

Intestinal permeability in exocrine pancreatic insufficiency due to cystic fibrosis or chronic pancreatitis

Disturbances of the intestinal integrity, reflected by an increased intestinal permeability, are reported in cystic fibrosis (CF). Controversy exists whether the increased intestinal permeability is due to CF itself or a consequence of the concomitant exocrine pancreatic insufficiency (PI). We measured intestinal permeability by the sugar absorption test in 32 PI patients: 20 CF-PI, 12 nonCF-PI with chronic pancreatitis, and 50 controls. In the sugar absorption test, the lactulose/mannitol ratio is measured in 5-h urine samples after oral ingestion of a solution of lactulose and mannitol, hyperosmolar by the addition of sucrose. The lactulose/mannitol ratio was increased in both CF-PI and nonCF-PI versus controls (p < 0.0001). In CF, the L/M ratio and permeability for lactulose and mannitol did not change by increasing pancreatic enzyme supplementation by 30-50% for 2 wk (p = 0.74, p = 0.97, p = 0.74, respectively) nor by decreasing the osmolarity of the test solution by 75% (p = 0.24, p = 0.10, p = 0.39, respectively). We conclude that an increased intestinal permeability in CF is probably a consequence of PI and is not related to the dose of pancreatic enzyme supplementation nor the osmolarity of the test solution. The increase is due to an increased permeability for lactulose which might point toward a defect in the tight junctions of the villi and/or crypts. The cause of the increased intestinal permeability in the presence of PI is still unclear. An increased intestinal permeability points toward an impaired functional integrity of the small bowel, which may contribute to gastrointestinal dysfunction in CF.

High frequency of celiac disease in Down syndrome

We screened 115 children with Down syndrome for celiac disease, using antigliadin, antiendomysium, and antireticulin serum antibodies and an intestinal permeability test. Celiac disease was diagnosed in eight children, giving a frequency of 7.0%. We recommend screening for celiac disease in all persons with Down syndrome, with the use of at least the antiendomysium antibody determination.

Gut permeability to human alpha-lactalbumin, beta-lactoglobulin, mannitol, and lactulose in celiac disease

Our objective was to examine the permeability of the gut to protein macromolecules and sugar probes and their possible association in celiac disease patients. We studied the permeability to human alpha-lactalbumin, beta-lactoglobulin, mannitol, and lactulose on 46 occasions in 33 celiac disease patients in various phases of the disease; in addition, mannitol and lactulose permeability was studied in 18 healthy controls. Lactalbumin absorption was detected in 19 of 42 patients tested, more often in celiac disease patients with villous atrophy than in those with normal jejunal biopsy (p = 0.01). Higher absorption of lactalbumin was found in patients with subtotal villous atrophy than in those with normal biopsy (p = 0.02). beta-lactoglobulin was found in four of 42 patients tested. Less mannitol was absorbed by patients with either subtotal or partial villous atrophy than by those with normal histology (p = 0.001 and 0.006, respectively). Lactulose recovery was higher in newly diagnosed patients and patients with subtotal villous atrophy than in controls (p = 0.007 and 0.03, respectively). The lactulose/mannitol ratio was higher in newly diagnosed patients and patients with villous atrophy than in controls (p = 0.002 and 0.002, respectively). The correlation between permeability to lactalbumin and mannitol and lactulose was poor. We conclude that permeability to proteins and sugar molecules is abnormal in celiac disease patients with mucosal damage and that they probably reflect different mechanisms of penetration.

Intestinal permeability testing in dogs with diet-responsive intestinal disease

Fifteen dogs with signs of small and, or, large bowel disease that responded clinically to an exclusion diet were studied, using differential sugar absorption as an objective parameter of the mucosal response to the diet. Intestinal permeability and function were assessed by determining the urinary excretion ratios of lactulose/rhamnose and xylose/3-O-methylglucose, respectively, following oral administration of a mixture of these four sugars. Five dogs, all retrievers, were tentatively diagnosed as having dietary hypersensitivity, based upon resolution of clinical signs and normalisation of high intestinal permeability following an exclusion diet and recurrence of signs (in four of five dogs) upon challenge with the original diet. The fifth dog did not become symptomatic when challenged, but intestinal permeability increased. The remaining 10 dogs were diagnosed as having food intolerance, based upon clinical improvement on an exclusion diet, relapse on challenge with their original diet, but lack of improvement in intestinal permeability. These findings suggest that a differential sugar absorption test may be useful to determine the reasons for clinical response to exclusion diets. Demonstration of increased intestinal permeability with subsequent normalisation following an exclusion diet may be useful in the diagnosis of dietary hypersensitivity, while persistent abnormalities in intestinal permeability are suggestive of underlying intestinal disease and food intolerance.

Early impairment of gut mucosal immunity in HIV-1-infected children

This study was performed in 27 HIV-1+ children to characterize the IgA hyperglobulinaemia observed in the serum during the course of HIV-1 infection. By contrast with serum IgG, which increased very early, IgA elevation was related to the decrease of CD4+ cell percentage. It was demonstrated that IgA1 subclass increased selectively. Secretory IgA (SIgA) and IgA and IgG activity to gliadin, bovine serum albumin (BSA) and at a lower level to casein could be detected in the serum at the early stages of HIV infection, but SIgA levels and IgA activity to gliadin further increased during the course of immunodeficiency. By contrast, IgA and IgG activity to tetanus toxoid did not change. These data demonstrate that the hyper IgA, closely related to the degree of immunodeficiency, could be due in part to a disturbance of the gut mucosal immune system. Moreover, impaired intestinal immunity seems to appear very early, and to progress during the course of paediatric HIV-1 infection.

A simple, non-invasive marker of gastric damage: sucrose permeability

Disaccharides do not cross intact gastrointestinal mucosa to any appreciable extent unless there is damage to the epithelium. Furthermore, since sucrose is rapidly broken down in the small intestine, the absorption of intact sucrose implies damage to proximal epithelium. We have reported that measurement of sucrose permeability detects gastric damage in animals. Whilst such a non-specific test could not replace endoscopy, it might represent a clinically useful technique to identify patients who would benefit from endoscopy. 189 patients underwent endoscopy and assessment of sucrose permeability to evaluate the effectiveness of increased sucrose permeability in the prediction of endoscopic findings. The endoscopist was blinded to results of the sucrose assay. Gastric damage, particularly ulcers and severe gastritis, was successfully detected with this technique. Increased sucrose permeability, however, did not reliably detect mild gastritis, oesophagitis, or duodenal disease. The sensitivity of the test for gastric ulceration was 84% and specificity in predicting an abnormal endoscopy was 96%. Measurement of sucrose permeability is a simple way of screening for gastric damage. It has a sensitivity similar to that for upper gastrointestinal radiology and provides a new way to effectively screen large populations at risk of gastric damage.