Comparison of four markers of intestinal permeability in control subjects and patients with coeliac disease

Impact of alcohol-induced intestinal microbiota dysbiosis in a rodent model of Alzheimer's disease

Introduction: Alzheimer's disease (AD) is a devastating neurodegenerative disorder. While genetics are important in the development of AD, environment and lifestyle are also important factors influencing AD. One such lifestyle factor is alcohol consumption. Unhealthy and excessive chronic alcohol consumption is associated with a greater risk of all types of dementia, especially AD. Alcohol consumption has numerous effects on the body, including alterations to the intestinal microbiota (dysbiosis) and intestinal barrier dysfunction (leakiness and intestinal hyperpermeability), with evidence indicating that inflammation resulting from dysbiosis and barrier dysfunction can promote neuroinflammation impacting brain structure and function. Objective: This study sought to determine the impact of alcohol-induced dysbiosis and barrier dysfunction on AD-like behavior and brain pathology using a transgenic rodent model of AD (3xTg-AD). Methods: Alcohol (20%) was administered to 3xTg-AD mice in the drinking water for 20 weeks. Intestinal (stool) microbiota, intestinal barrier permeability, systemic inflammation (IL-6), behavior, and AD pathology (phosphorylated tau and β-amyloid), and microglia were examined. Results: Alcohol consumption changed the intestinal microbiota community (dysbiosis) and increased intestinal barrier permeability in both control and 3xTg-AD mice (oral/urine sugar test and lipopolysaccharide-binding protein (LBP)). However, alcohol consumption did not influence serum IL-6, behavior, or β-amyloid, phosphorylated tau, or microglia in 3xTg-AD mice. Important differences in genotype and sex were noted. Conclusion: Alcohol-induced microbiota dysbiosis and intestinal barrier dysfunction did not exacerbate behavior or AD-like brain pathology in the 3xTg-AD mouse model of AD which could, in part, be the result of a lack of systemic inflammation.

Acute haemodynamic changes during haemodialysis do not exacerbate gut hyperpermeability

INTRODUCTION

The gastrointestinal tract is a potential source of inflammation in dialysis patients. In vitro studies suggest breakdown of the gut barrier in uraemia leading to increased intestinal permeability and it is hypothesised that haemodialysis exacerbates this problem due to mesenteric ischaemia induced by blood volume changes during treatment.

METHOD

The effect of haemodialysis on intestinal permeability was studied in ten haemodialysis patients and compared with five controls. Intestinal permeability was assessed by measuring the differential absorption of four orally administered sugar probes which provides an index of small and whole bowel permeability. A multi-sugar solution (containing lactulose, rhamnose, sucralose and erythritol) was orally administered after an overnight fast. Plasma levels of all sugar probes were measured hourly for 10 h post-administration. In haemodialysis patients, the procedure was carried out twice - once on a non-dialysis day and once immediately after haemodialysis.

RESULTS

Area under curve (AUC) for lactulose:rhamnose (L:R) ratio and sucralose:erythritol (S:E) ratio was similar post-dialysis and on non-dialysis days. AUC for L:R was higher in haemodialysis patients compared with controls (0.071 vs. 0.034, P=0.001), AUC for S:E ratio was not significantly different. Levels of lactulose, sucralose and erythritol were elevated and retained longer in haemodialysis patients compared with controls due to dependence of sugars on kidney function for clearance.

CONCLUSION

We found no significant acute changes in intestinal permeability in relation to the haemodialysis procedure. Valid comparison of intestinal permeability between controls and haemodialysis patients was not possible due to the strong influence of kidney function on sugar levels.

Assessing intestinal permeability in Crohn's disease patients using orally administered 52Cr-EDTA

Background

Intestinal permeability can be assessed by monitoring renal excretion of orally administered radioactively ⁵¹Cr-labeled ethylenediaminetetraacetic acid (⁵¹Cr-EDTA). Although considered safe, patient participation in using radio-labeled tracers is low. Here, we used orally administered ⁵²Cr-EDTA as non-radioactive alternative to assess intestinal permeability in CD and analyzed the association with disease activity, disease location and gut microbial dysbiosis.

Materials and methods

60 CD patients with low (n = 25) and increased (n = 35) fecal calprotectin levels (cut-off: 100 μg/g feces) ingested 20 mL ⁵²Cr-EDTA (20 mmol/L) solution whereafter 24-h urine was collected. Urinary ⁵²Cr-EDTA concentrations were quantified using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Fecal Enterobacteriaceae and Faecalibacterium prausnitzii were quantified using FISH. Correlations between urinary ⁵²Cr-EDTA excretion and other parameters were established using nonparametric Spearman’s correlation coefficients (ρ).

Results

CD patients with increased fecal calprotectin levels (> 100 μg/g) demonstrated an elevated urinary ⁵²Cr-EDTA/creatinine ratio (772 vs. 636 μmol/mol, P = 0.132). Patients with primarily colonic disease showed the highest ⁵²Cr-EDTA excretion. Importantly, a positive correlation was observed for the urinary ⁵²Cr-EDTA/creatinine ratio and fecal calprotectin levels (ρ = 0.325, P < 0.05). Finally, urinary ⁵²Cr-EDTA/creatinine ratio negatively correlated with the relative abundance of Faecalibacterium prausnitzii (ρ = -0.221, P = 0.092), while positively correlating with Enterobacteriaceae (ρ = 0.202, P = 0.126).

Conclusions

Orally administered and renal excreted ⁵²Cr-EDTA may be used to assess intestinal permeability in CD and correlates with fecal calprotectin levels and bacterial species relevant to CD. This test may improve non-invasive detection of disease exacerbations and help monitor disease activity.

Impact of gastrointestinal disease states on oral drug absorption – implications for formulation design – a PEARRL review

Objectives

Drug product performance in patients with gastrointestinal (GI) diseases can be altered compared to healthy subjects due to pathophysiological changes. In this review, relevant differences in patients with inflammatory bowel diseases, coeliac disease, irritable bowel syndrome and short bowel syndrome are discussed and possible in vitro and in silico tools to predict drug product performance in this patient population are assessed.

Key findings

Drug product performance was altered in patients with GI diseases compared to healthy subjects, as assessed in a limited number of studies for some drugs. Underlying causes can be observed pathophysiological alterations such as the differences in GI transit time, the composition of the GI fluids and GI permeability. Additionally, alterations in the abundance of metabolising enzymes and transporter systems were observed. The effect of the GI diseases on each parameter is not always evident as it may depend on the location and the state of the disease. The impact of the pathophysiological change on drug bioavailability depends on the physicochemical characteristics of the drug, the pharmaceutical formulation and drug metabolism. In vitro and in silico methods to predict drug product performance in patients with GI diseases are currently limited but could be a useful tool to improve drug therapy.

Summary

Development of suitable in vitro dissolution and in silico models for patients with GI diseases can improve their drug therapy. The likeliness of the models to provide accurate predictions depends on the knowledge of pathophysiological alterations, and thus, further assessment of physiological differences is essential.

Diurnal variations in intestinal barrier integrity and liver pathology in mice: implications for alcohol binge

Recent studies suggest that circadian rhythms regulate intestinal barrier integrity, but it is not clear whether there are daily variations in barrier integrity. This study investigated daily variations in intestinal barrier integrity, including whether there are differences in alcohol-induced intestinal barrier dysfunction after an alcohol binge at different times of day and whether this is associated with concurrent liver injury. C57BL6/J male mice were fed a standard chow diet, an alcohol-containing liquid diet, or an alcohol control diet for 4 wk. During week 5 (i.e., on days 43-45), mice received three once-daily gavages of alcohol (6 g/kg) or the control (phosphate-buffered saline) at the same time each day. Immediately after the binge on the second day, intestinal permeability was assessed. Four hours after the third and final binge, mice were euthanized and tissue samples collected. The results demonstrated diet-specific and outcome-specific effects of time, alcohol, and/or time by alcohol interaction. Specifically, the alcohol binge robustly influenced markers of intestinal barrier integrity, and liver markers were robustly influenced by time of day. Only intestinal permeability (i.e., sucralose) demonstrated a significant effect of time and also showed a binge by time interaction, suggesting that the time of the alcohol binge influences colonic permeability. NEW & NOTEWORTHY This study investigated daily variations in intestinal barrier integrity, including whether there are differences in alcohol-induced intestinal barrier dysfunction after an alcohol binge at different times of day and whether this is associated with concurrent liver injury. We conclude that 1) alcohol binge significantly impacted markers of intestinal permeability, 2) time of day significantly affected liver outcomes, and 3) the time of day influenced colonic permeability.

Expression Pattern of Fatty Acid Binding Proteins in Celiac Disease Enteropathy

Celiac disease (CD) is an immune-mediated enteropathy that develops in genetically susceptible individuals following exposure to dietary gluten. Severe changes at the intestinal mucosa observed in untreated CD patients are linked to changes in the level and in the pattern of expression of different genes. Fully differentiated epithelial cells express two isoforms of fatty acid binding proteins (FABPs): intestinal and liver, IFABP and LFABP, respectively. These proteins bind and transport long chain fatty acids and also have other important biological roles in signaling pathways, particularly those related to PPARγ and inflammatory processes. Herein, we analyze the serum levels of IFABP and characterize the expression of both FABPs at protein and mRNA level in small intestinal mucosa in severe enteropathy and normal tissue. As a result, we observed higher levels of circulating IFABP in untreated CD patients compared with controls and patients on gluten-free diet. In duodenal mucosa a differential FABPs expression pattern was observed with a reduction in mRNA levels compared to controls explained by the epithelium loss in severe enteropathy. In conclusion, we report changes in FABPs' expression pattern in severe enteropathy. Consequently, there might be alterations in lipid metabolism and the inflammatory process in the small intestinal mucosa.

Psychological stress and corticotropin-releasing hormone increase intestinal permeability in humans by a mast cell-dependent mechanism

OBJECTIVE

Intestinal permeability and psychological stress have been implicated in the pathophysiology of IBD and IBS. Studies in animals suggest that stress increases permeability via corticotropin-releasing hormone (CRH)-mediated mast cell activation. Our aim was to investigate the effect of stress on intestinal permeability in humans and its underlying mechanisms.

DESIGN

Small intestinal permeability was quantified by a 2 h lactulose-mannitol urinary excretion test. In a first study, 23 healthy volunteers were subjected to four different conditions: control; indomethacin; public speech and anticipation of electroshocks. In a second study, five test conditions were investigated in 13 volunteers: control; after pretreatment with disodium cromoglycate (DSCG); administration of CRH; DSCG+CRH and DSCG+public speech.

RESULTS

Indomethacin, as a positive comparator (0.071±0.040 vs 0.030±0.022; p<0.0001), and public speech (0.059±0.040; p<0.01), but not the shock protocol increased intestinal permeability. Similarly, salivary cortisol was only increased after public speech. Subgroup analysis demonstrated that the effect of public speech on permeability was only present in subjects with a significant elevation of cortisol. CRH increased the lactulose-mannitol ratio (0.042±0.021 vs 0.028±0.009; p=0.02), which was inhibited by the mast cell stabiliser DSCG. Finally, intestinal permeability was unaltered by public speech with DSCG pretreatment.

CONCLUSIONS

Acute psychological stress increases small intestinal permeability in humans. Peripheral CRH reproduces the effect of stress and DSCG blocks the effect of both stress and CRH, suggesting the involvement of mast cells. These findings provide new insight into the complex interplay between the central nervous system and GI function in man.

Modulation of gut barrier function in patients with obstructive jaundice using probiotic LP299v

OBJECTIVES

This study aimed to determine the effect of LP229v on intestinal permeability and tumour necrosis factor (TNF) p55 receptor concentrations in patients with obstructive jaundice undergoing biliary drainage.

PATIENTS AND METHODS

Patients undergoing biliary drainage were recruited and randomized into three groups to receive Lactobacillus plantarum 299v (LP299v), inactivated LP299v (placebo) or water. These were administered daily at noon until 7 days after biliary drainage. Intestinal permeability was measured using the lactulose/mannitol (L/M) dual sugar absorption test on admission, the day before biliary drainage and on days 1 and 7 after biliary drainage. Blood and urine were collected to determine the L/M ratio and the TNF p55 receptor levels at each time point.

RESULTS

A total of 25 patients were recruited; 12 had choledocholithiasis and nine had a periampullary tumour. Open surgical biliary drainage was performed in nine patients, endoscopic retrograde cholangiopancreatography in 12 and percutaneous transhepatic cholangiography in two. Five patients received LP299v, five received placebo and seven, water. The median L/M ratio was 0.035 (0.018-0.065) at baseline. No difference existed between the groups on admission, before drainage and on day 7 after drainage (P=0.59, 0.175 and 0.61, respectively). The L/M ratio was lower in the LP299v group on day 1 after drainage [0.01 (0.01) vs. 0.18 (0.03-0.3) and 0.11 (0.07-0.14); P=0.37]. Although the TNF p55 receptor levels were lower on day 1 after drainage in the LP299v group (15.3 vs. 30.9 vs. 82.7 ng/ml; P=0.43), the concentration at the four time points was similar (P=0.24, 0.96, 0.43 and 0.68).

CONCLUSION

Pretreatment with probiotic LP299v improves intestinal permeability after biliary drainage and attenuates the inflammatory response. However, a larger multicentre trial is required to determine the effect on clinical outcome.

Quantitative assessment of altered rectal mucosal permeability due to rectally applied nonoxynol-9, biopsy, and simulated intercourse

BACKGROUND

Microbicide toxicity may reduce the efficacy of topical preexposure prophylaxis for human immunodeficiency virus (HIV) transmission. Noninvasive quantitative measures of microbicide toxicity would usefully inform microbicide development.

METHODS

Ten subjects received 3 one-time interventions: 5 mL of Normosol-R fluid alone (negative control), 5 mL of 2% nonoxynol-9 (N-9) gel, and 5 mL of Normosol-R with coital simulation and sigmoidoscopic biopsy (CS + BX). Each dose of N-9 and Normosol-R contained 500 µCi of (99m)technetium-diethylene triamine pentaacetic acid. Plasma and urine radioactivity was assessed over 24 hours.

RESULTS

The plasma radioisotope concentration peaked 1 hour after N-9 dosing. The mean maximum radioisotope concentration after N-9 receipt was 12.0 times (95% confidence interval [CI], 6.8-21.0) and 8.4 times (95% CI, 5.2-13.5) the mean concentration after Normosol-R control receipt and CS + BX receipt, respectively; paired differences persisted for 24 hours. After N-9 dosing, the urine isotope level was 3.6 times (95% CI, 1.1-11.4) the level observed 8 hours after Normosol-R control receipt and 4.0 times (95% CI, 1.4-11.4) the level observed 4 hours after CS + BX receipt. Permeability after CS + BX receipt was greater than that after Normosol-R control receipt in 0-2-hour urine specimens only (mean permeability, 2.4; 95% CI, 1.0-5.8) but was not greater in blood.

CONCLUSIONS

Plasma sampling after rectal radioisotope administration provided quantitative estimates of altered mucosal permeability after chemical and mechanical stresses. Permeability testing may provide a useful noninvasive adjunct to assess the mucosal effects of candidate microbicides. Clinical Trials Registration. NCT00389311.

Polyethylene glycol versus dual sugar assay for gastrointestinal permeability analysis: is it time to choose?

Background

Increased intestinal permeability is an important measure of disease activity and prognosis. Currently, many permeability tests are available and no consensus has been reached as to which test is most suitable. The aim of this study was to compare urinary probe excretion and accuracy of a polyethylene glycol (PEG) assay and dual sugar assay in a double-blinded crossover study to evaluate probe excretion and the accuracy of both tests.

Methods

Gastrointestinal permeability was measured in nine volunteers using PEG 400, PEG 1500, and PEG 3350 or lactulose-rhamnose. On 4 separate days, permeability was analyzed after oral intake of placebo or indomethacin, a drug known to increase intestinal permeability. Plasma intestinal fatty acid binding protein and calprotectin levels were determined to verify compromised intestinal integrity after indomethacin consumption. Urinary samples were collected at baseline, hourly up to 5 hours after probe intake, and between 5 and 24 hours. Urinary excretion of PEG and sugars was determined using high-pressure liquid chromatography-evaporative light scattering detection and liquid chromatography-mass spectrometry, respectively.

Results

Intake of indomethacin increased plasma intestinal fatty acid-binding protein and calprotectin levels, reflecting loss of intestinal integrity and inflammation. In this state of indomethacin-induced gastrointestinal compromise, urinary excretion of the three PEG probes and lactulose increased compared with placebo. Urinary PEG 400 excretion, the PEG 3350/PEG 400 ratio, and the lactulose/rhamnose ratio could accurately detect indomethacin-induced increases in gastrointestinal permeability, especially within 2 hours of probe intake.

Conclusion

Hourly urinary excretion and diagnostic accuracy of PEG and sugar probes show high concordance for detection of indomethacin-induced increases in gastrointestinal permeability. This comparative study improves our knowledge of permeability analysis in man by providing a clear overview of both tests and demonstrates equivalent performance in the current setting.

Novel analytical approach to a multi-sugar whole gut permeability assay

Many pathophysiological conditions are associated with increased gastrointestinal permeability, reflecting an elevated risk of endotoxaemia, inflammation, and sepsis. Permeability tests are increasingly used in clinical practice to obtain information on gastrointestinal functioning, but tests are often restricted to the small intestine, and require large oral sugar doses. Therefore, a novel multi-sugar assay was developed, allowing assessment of whole gut permeability changes in urinary and plasma samples collected at regular intervals from 10 healthy volunteers at baseline and after intake of monosaccharides (rhamnose and erythritol) and disaccharides (sucrose, lactulose, and sucralose). Samples were analyzed by isocratic cation-exchange LC-MS. Sample preparation and detection conditions were optimized. After centrifugation, chromatographic separation was achieved on an IOA-1000 column set at 30°C. Column effluent was mixed with ammonia for sugar-ammonium adduct formation. The lower limit of detection was 0.05 μmol/L for disaccharides and 0.1 μmol/L for monosaccharides. Linearity for each probe was between 1 and 1000 μmol/L (R(2): 0.9987-0.9999). Coefficients of variation were <5% in urine, and <9% in plasma. Recovery data were within the 90% to 110% range at all spiked concentrations. This highly sensitive novel LC-MS approach resulted in a significant decrease of the detection limit for all sugar probes, allowing a 5-fold reduction of the commonly used lactulose dose and the addition of sugar probes to also assess the gastroduodenal and colon permeability. In combination with its extended application in plasma, these features make the novel assay a promising tool in the assessment of site-specific changes in gastrointestinal permeability in clinical practice.

Efficacy of various dietary calcium salts to improve intestinal resistance to Salmonella infection in rats

Previous animal and human studies have shown protective effects of Ca on the resistance to enteropathogenic infections. Most interventions were performed with calcium phosphate and little is known about the protective effect of other dietary sources of Ca. Therefore, we investigated the efficacy of several Ca salts to enhance intestinal resistance to Salmonella enteritidis infection. Rats (n 7–8 per group) were fed a high-fat, Western human-style, purified diet with a low Ca content (20 mmol calcium phosphate/kg; negative control group) or the same diet supplemented with either (extra) calcium phosphate, milk Ca, calcium chloride or calcium carbonate (total of 100 mmol Ca supplement/kg). Diets contained Cr-EDTA for assessment of incremental changes in intestinal permeability. After an adaptation period of 2 weeks, animals were orally infected with S. enteritidis to mimic a human-relevant foodborne infection. Ca supplement-induced changes on faecal lactobacilli and enterobacteria were studied before infection. Changes in intestinal permeability were determined by measuring urinary Cr with time. Persistence of Salmonella was determined by studying faecal excretion of this pathogen in time. Overall, all Ca salts increased resistance towards Salmonella. After infection, body weight gain and food intake were higher in the calcium phosphate group. Calcium phosphate and milk Ca decreased faecal enterobacteria before infection. All Ca salts decreased infection-induced intestinal permeability and persistence of Salmonella. Calcium phosphate, milk Ca, calcium carbonate and calcium chloride are able to enhance the intestinal resistance to Salmonella in rats.

PPAR-alpha Contributes to the Anti-Inflammatory Activity of Verbascoside in a Model of Inflammatory Bowel Disease in Mice

The previous results suggest that peroxisome proliferator-activated receptor-alpha (PPAR)-α, an intracellular transcription factor activated by fatty acids, plays a role in control of inflammation. There is persuasive epidemiological and experimental evidence that dietary polyphenols have anti-inflammatory activity. In this regard, it has been demonstrated that verbascoside (VB) functions as intracellular radical scavenger and reduces the microscopic and macroscopic signs of experimental colitis. With the aim to characterize the role of PPAR-α in VB-mediated anti-inflammatory activity, we tested the efficacy of VB in an experimental model of inflammatory bowel disease induced by dinitrobenzene sulfonic acid, comparing mice lacking PPAR-α (PPAR-αKO) with wild type (WT) mice. Results indicate that VB-mediated anti-inflammatory activity is weakened in PPAR-αKO mice, compared to WT controls, especially in the inhibition of neutrophil infiltration, intestinal permeability and colon injury. These results indicate that PPAR-α can contribute to the anti-inflammatory activity of VB in inflammatory bowel disease.

Intestinal barrier gene variants may not explain the increased levels of antigliadin antibodies, suggesting other mechanisms than altered permeability

Various genes may influence intestinal barrier function, including MAGI2, MYO9B, and PARD3, which are associated with celiac disease. Because direct measurement of intestinal permeability is difficult, antibodies against gliadin (AGA) and Baker's yeast (anti-Saccharomyces cerevisiae antibodies [ASCA]) can be used as an indirect test. The objective of this study was to investigate whether intestinal permeability, represented by AGA, was correlated with MAGI2, MYO9B, and PARD3. Analyses were performed in patients with Down syndrome, a population with suspected increased intestinal permeability. Correlations between AGA and ASCA were investigated. Patients with Down syndrome (n = 126) were genotyped for six single-nucleotide polymorphisms in MAGI2 (rs1496770, rs6962966, rs9640699), MYO9B (rs1457092, rs2305764), and PARD3 (rs10763976). An allele dosage association of these risk genes and AGA levels was performed. The correlation between AGA and ASCA was studied. A strong correlation was found between AGA and ASCA (p < 0.01). The patient group with one or more risk genotypes had lower mean AGA levels (trend test p = 0.007) and consisted of a larger number of patients with normal AGA levels (p = 9.3 x 10(-5)). Celiac-associated risk genotypes are associated with lower AGA values instead of elevated ones. Thus, other immunologic phenomena play a role in the increased prevalence of elevated AGA in patients with Down syndrome, possibly involving altered induction and/or maintenance of tolerance.

Non-invasive investigation in patients with inflammatory joint disease

Gut inflammation can occur in 30%-60% of patients with spondyloarthropathies. However, the presence of such gut inflammation is underestimated, only 27% of patients with histological evidence of gut inflammation have intestinal symptoms, but subclinical gut inflammation is documented in two-thirds of patients with inflammatory joint disease. There are common genetic and immunological mechanisms behind concomitant inflammation in the joints and intestinal tract. A number of blood tests, e.g. erythrocyte sedimentation rate, orosomucoid, C-reactive protein, and white cell and platelet counts, are probably the most commonly used laboratory markers of inflammatory disease, however, these tests are difficult to interpret in arthropathies associated with gut inflammation, since any increases in their blood levels might be attributable to either the joint disease or to gut inflammation. Consequently, it would be useful to have a marker capable of separately identifying gut inflammation. Fecal proteins, which are indirect markers of neutrophil migration in the gut wall, and intestinal permeability, seem to be ideal for monitoring intestinal inflammation: they are easy to measure non-invasively and are specific for intestinal disease in the absence of gastrointestinal infections. Alongside the traditional markers for characterizing intestinal inflammation, there are also antibodies, in all probability generated by the immune response to microbial antigens and auto-antigens, which have proved useful in establishing the diagnosis and assessing the severity of the condition, as well as the prognosis and the risk of complications. In short, non-invasive investigations on the gut in patients with rheumatic disease may be useful in clinical practice for a preliminary assessment of patients with suspected intestinal disease.

Intestinal barrier function in response to abundant or depleted mucosal glutathione in Salmonella-infected rats

Background

Glutathione, the main antioxidant of intestinal epithelial cells, is suggested to play an important role in gut barrier function and prevention of inflammation-related oxidative damage as induced by acute bacterial infection. Most studies on intestinal glutathione focus on oxidative stress reduction without considering functional disease outcome. Our aim was to determine whether depletion or maintenance of intestinal glutathione changes susceptibility of rats to Salmonella infection and associated inflammation.

Rats were fed a control diet or the same diet supplemented with buthionine sulfoximine (BSO; glutathione depletion) or cystine (glutathione maintenance). Inert chromium ethylenediamine-tetraacetic acid (CrEDTA) was added to the diets to quantify intestinal permeability. At day 4 after oral gavage with Salmonella enteritidis (or saline for non-infected controls), Salmonella translocation was determined by culturing extra-intestinal organs. Liver and ileal mucosa were collected for analyses of glutathione, inflammation markers and oxidative damage. Faeces was collected to quantify diarrhoea.

Results

Glutathione depletion aggravated ileal inflammation after infection as indicated by increased levels of mucosal myeloperoxidase and interleukin-1β. Remarkably, intestinal permeability and Salmonella translocation were not increased. Cystine supplementation maintained glutathione in the intestinal mucosa but inflammation and oxidative damage were not diminished. Nevertheless, cystine reduced intestinal permeability and Salmonella translocation.

Conclusion

Despite increased infection-induced mucosal inflammation upon glutathione depletion, this tripeptide does not play a role in intestinal permeability, bacterial translocation and diarrhoea. On the other hand, cystine enhances gut barrier function by a mechanism unlikely to be related to glutathione.

The use of Cellomics to study enterocyte cytoskeletal proteins in coeliac disease patients

Coeliac disease is characterised by inflammation of small intestinal mucosa accompanied by abnormal villous architecture. It is now accepted that some patients with positive coeliac serology tests may have minor mucosal lesions that may not be apparent on routine histopathological analysis. The aim of the study was to perform detailed examination of enterocyte morphology and cytoskeletal structures using a high content analysis technology. Duodenal biopsies from 14 untreated and 10 treated coeliac patients and from 20 non-coeliac controls were examined. Tissue sections from six patients (study group subjects) before and after the development of gluten-sensitive enteropathy were also investigated. Immunohistochemical studies were performed on paraffin-embedded sections using an anti-α-tubulin antibody. Significant differences in enterocyte morphology and intracellular cytoskeletal structures were demonstrated in patients with proven coeliac disease and in the study group subjects. These changes were present in study group biopsies before evidence of enteropathy, as assessed by routine microscopy. This is the first study to demonstrate detailed characteristics of enterocyte morphology in coeliac patients using a high content analysis approach. The use of this technology allows a quantitative analysis of enterocyte intracellular structures from routine biopsy material and permits detection of subtle changes that precede the characteristic histological lesion.

The digestive adaptation of flying vertebrates: high intestinal paracellular absorption compensates for smaller guts

Anecdotal evidence suggests that birds have smaller intestines than mammals. In the present analysis, we show that small birds and bats have significantly shorter small intestines and less small intestine nominal (smooth bore tube) surface area than similarly sized nonflying mammals. The corresponding >50% reduction in intestinal volume and hence mass of digesta carried is advantageous because the energetic costs of flight increase with load carried. But, a central dilemma is how birds and bats satisfy relatively high energy needs with less absorptive surface area. Here, we further show that an enhanced paracellular pathway for intestinal absorption of water-soluble nutrients such as glucose and amino acids may compensate for reduced small intestines in volant vertebrates. The evidence is that l-rhamnose and other similarly sized, metabolically inert, nonactively transported monosaccharides are absorbed significantly more in small birds and bats than in nonflying mammals. To broaden our comparison and test the veracity of our finding we surveyed the literature for other similar studies of paracellular absorption. The patterns found in our focal species held up when we included other species surveyed in our analysis. Significantly greater amplification of digestive surface area by villi in small birds, also uncovered by our analysis, may provide one mechanistic explanation for the observation of higher paracellular absorption relative to nonflying mammals. It appears that reduced intestinal size and relatively enhanced intestinal paracellular absorption can be added to the suite of adaptations that have evolved in actively flying vertebrates.

Recent advances in the understanding of celiac disease: therapeutic implications for the management of pediatric patients

Celiac disease (CD) is an autoimmune condition occurring in genetically susceptible individuals characterized by inflammatory injury to the mucosa of the small intestine after the ingestion of wheat glutens or related barley and rye products. Originally thought to be highly prevalent only in Northern European populations, growing evidence indicates a much higher prevalence in many other regions, including the US as well as South America, North Africa, and Asia. The growing awareness that pediatric patients may present with quite diverse and protean manifestations and the significant impact of CD on childhood development has prompted efforts to increase CD awareness for the early diagnosis and treatment of this disease. The current diagnostic criteria for CD requires characteristic histologic findings in small bowel biopsies and clinical remission when placed on a gluten-free diet. Serologic testing for CD can provide additional support for the diagnosis of CD or a means to assess efficacy and adherence to a gluten-free diet. The mainstay of treatment remains the institution of a gluten-free diet. However, patients with refractory CD may require treatment with immunosuppressant medications. With the increased identification of specific gluten epitopes and understanding of the pathogenesis of CD, future therapies may rely on genetically altering gluten proteins, immunization techniques, or therapies focused on either the development of specific immune tolerance or regulation of mucosal inflammation.

Resolution of common dietary sugars from probe sugars for test of intestinal permeability using capillary column gas chromatography

BACKGROUND

The most widely accepted method for the evaluation of intestinal barrier integrity is the measurement of the permeation of sugar probes following an oral test dose of sugars. The most-widely used sugar probes are sucrose, lactulose, mannitol and sucralose. Measuring these sugars using a sensitive gas chromatographic (GC) method, we noticed interference on the area of the lactulose and mannitol peaks.

METHODS

We tested different sugars to detect the possible makeup of these interferences and finally detected that the lactose interferes with lactulose peak and fructose interferes with mannitol peak. On further developing of our method, we were able to reasonably separate these peaks using different columns and condition for our assay. Sample preparation was rapid and simple and included adding internal standard sugars, derivitization and silylation. We used two chromatographic methods. In the first method we used Megabore column and had a run time of 34 min. This resulted in partial separation of the peaks. In the second method we used thin capillary column and was able to reasonably separate the lactose and lactulose peaks and the mannitol and fructose peaks with run time of 22 min.

RESULTS

The sugar probes including mannitol, sucrose, lactulose, sucralose, fructose and lactose were detected precisely, without interference. The assay was linear between lactulose concentrations of 0.5 and 40 g/L (r(2)=1.000, P<0.0001) and mannitol concentrations of 0.01 and 40 g/L (r(2)=1.000). The sensitivity of this method remained high using new column and assay condition. The minimum detectable concentration calculated for both methods was 0.5 mg/L for lactulose and 1 mg/L for mannitol.

CONCLUSION

This is the first report of interference of commonly used sugars with test of intestinal permeability. These sugars are found in most of fruits and dairy products and could easily interfere with the result of permeability tests. Our new GC assay of urine sugar probes permits the simultaneous quantitation of sucralose, sucrose, mannitol and lactulose, without interference with lactose and fructose. This assay is a rapid, simple, sensitive and reproducible method to accurately measure intestinal permeability.

5-Lipoxygenase modulates colitis through the regulation of adhesion molecule expression and neutrophil migration

Leukotrienes play a part in inflammatory response. The unique role of the enzyme 5-lipoxygenase (5-LO) in the production of leukotrienes makes it as therapeutic target for inflammatory conditions like inflammatory bowel disease (IBD). In the present study, by comparing the responses in wild-type mice (5-LOWT) and mice lacking the 5-lipoxygenase (5-LOKO), we investigated the role played by this enzyme in the development of experimental colitis. To address this question, we used an experimental model of colitis, induced by dinitrobenzene sulfonic acid (DNBS). When compared to DNBS-treated 5-LOWT mice, DNBS-treated 5-LOKO mice experienced a reduced rate of the extent and severity of the histological signs of colon injury. After administration of DNBS 5-LOWT mice showed hemorrhagic diarrhea, weight loss and large areas of necrosis in the mucosa of the colon. Neutrophil infiltration was associated with the expression of ICAM-1, VCAM-1, P-selectin, E-selectin that were mainly localized around vessels. Absence of a functional 5-LO resulted in a significant reduction of all the above-described parameters. In particular, we have observed a significant reduction of: (i) the degree of colon injury, (ii) the rise in myeloperoxidase (MPO) activity (mucosa), (iii) the increase in staining (immunohistochemistry) for ICAM-1, VCAM-1, P-selectin, E-selectin caused by DNBS in the colon. Similarly, the treatment of 5-LOWT with zileuton (50 mg/kg per os twice a day) resulted in a significant reduction of all the above-described parameters. In addition, in in vitro study a significantly reduced chemotactic response to IL-8 was observed in peripheral blood leukocytes from 5-LOKO in comparison to 5-LOWT polymorphonuclear leukocyte. Similar results were obtained when we analyzed the chemotactic response of 5-LOWT cell incubated for 15 min with zileuton (50 microg/ml). Taken together, our results clearly demonstrate that 5-LO modulates neutrophil infiltration in experimental colitis through the expression of adhesion molecules.

Dietary fructooligosaccharides increase intestinal permeability in rats

We showed previously that fructooligosaccharides (FOS) decrease the resistance to salmonella infection in rats. However, the mechanism responsible for this effect is unclear. Therefore, we examined whether dietary FOS affects intestinal permeability before and after infection with Salmonella enterica serovar Enteritidis. Male Wistar rats were fed restricted quantities of a purified diet that mimicked the composition of a Western human diet. The diet was supplemented with 60 g/kg cellulose (control) or 60 g/kg FOS and with 4 mmol/kg of the intestinal permeability marker chromium EDTA (CrEDTA) (n = 8 or 10). After an adaptation period of 2 wk, rats were orally infected with 10(8) colony-forming units (cfu) of S. enteritidis. Mucin concentrations in intestinal contents and mucosa were measured fluorimetrically, as markers of mucosal irritation. Intestinal permeability was determined by measuring urinary CrEDTA excretion. Translocation of salmonella was quantified by analysis of urinary nitric oxide metabolites with time. Before infection, FOS increased mucosal lactobacilli and enterobacteria in cecum and colon, but not in the ileum. However, FOS increased cytotoxicity of fecal water and intestinal permeability. Moreover, FOS increased fecal mucin excretion and mucin concentrations in cecal and colonic contents, and in cecal mucosa before infection. After infection, mucin excretion and intestinal permeability in the FOS groups increased even further in contrast to the control group. In addition, FOS increased translocation of salmonella to extraintestinal sites. Thus, FOS impairs the intestinal barrier in rats, as indicated by higher intestinal permeability. Whether these results can be extrapolated to humans requires further investigation.

Pharmacology and gastrointestinal safety of lumiracoxib, a novel cyclooxygenase-2 selective inhibitor: An integrated study

BACKGROUND AND AIMS

Lumiracoxib is a structurally novel, acidic selective inhibitor of cyclooxygenase (COX)-2. We coordinated existing methodologies in a single study to evaluate potency, selectivity, and effect on the human gastrointestinal tract.

METHODS

Twenty four healthy subjects (aged 18-45 years, 12 female) received high dose lumiracoxib (800 mg every day), standard dose naproxen (500 mg twice a day), or placebo for 8 days in a double-blind randomized crossover study. At the start and end of each dosing period, COX-2 selectivity was assessed by ex vivo serum thromboxane B(2) (COX-1) and lipopolysaccharide stimulated prostaglandin (PG) E(2) (COX-2), mucosal injury by endoscopy, and small and large bowel permeability by 0- to 5-hour and 5- to 24-hour (51)Cr-EDTA absorption. Plasma lumiracoxib was measured 2 hours after dosing on day 8 and vortex-stimulated ex vivo gastric mucosal PGE(2) synthesis at the end of each treatment period by enzyme immunoassay.

RESULTS

Lumiracoxib was well absorbed and demonstrated similar potency to naproxen as a COX-2 inhibitor (77% and 66% inhibition, respectively, vs. placebo), but it differed in being more selective (24% and 97% inhibition of thromboxane B(2) vs. placebo). Gastric PGE(2) was reduced by 69% by naproxen (P < 0.001 vs. placebo) and 29% by lumiracoxib (P < 0.01 vs. placebo and naproxen). No subjects developed gastroduodenal erosions on lumiracoxib (vs. 75% on naproxen and 12.5% on placebo). (51)Cr-EDTA absorption increased significantly with naproxen but not lumiracoxib.

CONCLUSIONS

Lumiracoxib is a potent selective inhibitor of COX-2 that causes little or no endoscopically detected stomach or duodenal injury or changes in bowel permeability.

Lactulose/mannitol test has high efficacy for excluding organic causes of chronic diarrhea

OBJECTIVES

Diagnosis in chronic diarrhea in the absence of a distinctive clinical pattern is often challenging, as biochemical tests prescribed at the first evaluation do not show enough sensitivity and specificity to tailor further investigation. Intestinal permeability to sugars is an accurate test for detecting intestinal damage. The aim of this study was to evaluate the diagnostic value of the lactulose/mannitol (L/M) test in patients with chronic diarrhea.

METHODS

We conducted a prospective cohort study to evaluate the diagnostic value of the L/M test in chronic diarrhea. The test was administered to 261 consecutive patients presenting with three or more bowel movements daily for at least 3 wk. Biochemical tests including complete blood cell count, acute phase reactive proteins, serum albumin and iron, and stool cultures for bacteria, ova, and parasites were assessed at the same time. Additional diagnostic investigations were directed by clinical features as well as first-line test results.

RESULTS

Over 3 yr, 120 (46%) of our patients were found to have an organic cause for chronic diarrhea, whereas in 141 (54%) a functional condition was diagnosed. Multivariate logistic regression analysis revealed that the L/M test and C-reactive protein were independent predictors for the final diagnosis of organic cause of chronic diarrhea, with odds ratios of 1.5 (95% CI = 1.29-1.78) and 5.2 (95% CI = 1.90-14.12), respectively. The area under the receiver operating characteristic (ROC) curve of the adjusted model was 0.82, with positive predictive value of 80.4% and negative predictive value of 77.7%.

CONCLUSIONS

The L/M test is a powerful tool for workup in patients with chronic diarrhea. Introducing the L/M test as first-level test effectively improves the selection of patients who need further evaluation.

Postinfectious irritable bowel syndrome

A small but significant subgroup of patients with irritable bowel syndrome (IBS) report a sudden onset of their IBS symptoms after a bout of gastroenteritis. Population-based surveys show that although a history of neurotic and psychologic disorders, pain-related diseases, and gastroenteritis are all risk factors for developing IBS, gastroenteritis is the most potent. More toxigenic organisms increase the risk 11-fold, as does an initial illness lasting more than 3 weeks. Hypochondriasis and adverse life events double the risk for postinfective (PI)-IBS and may account for the increased proportion of women who develop this syndrome. PI-IBS is associated with modest increases in mucosal T lymphocytes and serotonin-containing enteroendocrine cells. Animal models and some preliminary human data suggest this leads to excessive serotonin release from the mucosa. Both the histologic changes and symptoms in humans may last for many years with only 40% recovering over a 6-year follow-up. Celiac disease, microscopic colitis, lactose intolerance, early stage Crohn's disease, and bile salt malabsorption should be excluded, as should colon cancer in those over the age of 45 years or in those with a positive family history. Treatment with Loperamide, low-fiber diets, and bile salt- binding therapy may help some patients. Serotonin antagonists are logical treatments but have yet to be evaluated.

In vivo influence of nicotine on human basal and NSAID-induced gut barrier function

BACKGROUND

Smoking reduces the non-steroidal anti-inflammatory drug (NSAID)-induced small intestinal permeability increase in healthy people. It also affects inflammatory bowel disease that is associated with a disturbed gut barrier function. To assess the role of nicotine on barrier function, its influence on basal and NSAID-induced intestinal permeability was studied in healthy volunteers.

METHODS

Thirty-one healthy non-smoker subjects performed permeability tests with 51Cr-EDTA and sugar markers (sucrose, lactulose, mannitol, sucralose) before and during 2 weeks of nicotine patch application, and with and without indomethacin intake, respectively. Since smoking has been described as affecting motility, transit measurements were also done with the sodium[13C]-octanoate and lactose-[13C]-ureide breath tests before and during nicotine exposure. Correlations between permeability markers were checked and the influence of gastrointestinal transit was assessed.

RESULTS

Nicotine did not affect barrier function in vivo, nor gastric emptying, small-bowel transit time or orocaecal transit. 51Cr-EDTA and lactulose correlated in basal 0-6 h permeability testing (r = 0.529, P < 0.0001), as did 6-24 h excretion of 51Cr-EDTA and sucralose (r = 0.474, P < 0.001); 97% and 90% of the subjects had a permeability increase after indomethacin intake for 0-6 h and 6-24 h excretion of Cr-EDTA, respectively. This population proportion is 63% for lactulose/mannitol and 83% for sucralose.

CONCLUSIONS

Short-term exposure to nicotine does not alter normal basal or NSAID-induced gut barrier function or transit. 51Cr-EDTA and the respective sugar markers correlate well in in vivo permeability testing in healthy humans. The radioactive test detects more NSAID-induced permeability increase than does the lactulose/mannitol ratio permeability test.

Gas chromatographic method for detection of urinary sucralose: application to the assessment of intestinal permeability

We developed a capillary column gas chromatography (CCGC) method for the measurement of urinary sucralose (S) and three other sugar probes including, sucrose, lactulose (L) and mannitol (M) for use in in vivo studies of intestinal permeability. We compared the capillary method with a packed column gas chromatography (PCGC) method. We also investigated a possible role for sucralose as a probe for the measurement of whole gut permeability. Sample preparation was rapid and simple. The above four sugars were detected precisely, without interference. We measured intestinal permeability using 5- and 24-h urine collections in 14 healthy volunteers. The metabolism of sugars was evaluated by incubating the intestinal bacteria with an iso-osmolar mixture of mannitol, lactulose and sucralose at 37 degrees C for 19 h. Sugar concentrations and the pH of the mixture were monitored. The use of the CCGC method improved the detection of sucralose as compared to PCGC. The average coefficient of variation decreased from 15% to 4%. It also increased the sensitivity of detection by 200-2000-fold. The GC assay was linear between sucralose concentrations of 0.2 and 40 g/l (r=1.000). Intestinal bacteria metabolized lactulose and acidified the media but did not metabolize sucralose or mannitol. The new method for the measurement of urinary sucralose permits the simultaneous quantitation of sucrose, mannitol and lactulose, and is rapid, simple, sensitive, accurate and reproducible. Because neither S nor M is metabolized by intestinal bacteria, and because only a tiny fraction of either sugar is absorbed, this pair of sugar probes appears to be available for absorption throughout the GI tract. Thus, the 24-h urinary concentrations of S and M, or the urinary S/M ratio following an oral dose of a sugar mixture, might be good markers for whole gut permeability.

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.

Intestinal permeability in adult patients with growth hormone deficiency

Pathological disruption of the intestinal mucosa increases the paracellular pathway, leading to an increase in the penetration of large molecules. Since growth hormone (GH) has a trophic intestinal effect, we used a double marker test to enable examination of intestinal permeability, which reflects the state of integrity of the intestinal mucosa. We recruited 22 adult patients, mean age 54+/-13.3 years, with GH deficiency due to partial or total hypopituitarism. None had received GH treatment at any time, although they were all in optimized replacement therapy. A control group was composed of 19 healthy age-matched relatives. The intestinal permeability test was performed with lactulose (5 g) and mannitol (1 g) after an oral load of 100 ml of aqueous solution. The urinary lactulose/mannitol ratio and the percentages of lactulose and mannitol excreted were determined on a 5-h urine collection. There were no significant differences between the patients and the control group in the lactulose/mannitol ratio (0.087+/-0.059 vs 0.077+/-0.064, respectively) or in the urinary excretion percentages of lactulose (0.067+/-0.048% vs 0.073+/-0.070%, respectively) or mannitol (5.127+/-3.269% vs 5.068+/-2.985%, respectively). In conclusion, no increase in intestinal permeability was detected in patients with GH deficiency, so that in spite of the known trophic effects of GH on the epithelial crypt cells, there was no intestinal hyperpermeability in these patients.

The prevalence and severity of intestinal disaccharidase deficiency in human immunodeficiency virus-infected subjects

BACKGROUND

Gastrointestinal symptoms are distressing features of human immunodeficiency virus (HIV) infection, and management is often empirical, including withdrawal of dietary lactose. We assessed the prevalence and severity of intestinal disaccharidase deficiency in vitro and in vivo.

METHODS

Fifty-four HIV-seropositive patients (19 HIV well +/- mild diarrhoea, 7 acquired immunodeficiency syndrome (AIDS) well, and 28 AIDS with diarrhoea) were studied with a combined non-invasive absorption-permeability-disaccharidase test that enables quantitative assessment of the rate of intestinal hydrolysis of lactose, sucrose, and palatinose. Thirty patients had jejunal biopsy specimens suitable for histomorphometric assessment, and 36 had in vitro disaccharidase activity measurement.

RESULTS

Patients with HIV (with mild diarrhoea) and AIDS (with and without severe diarrhoea) had frequent but mild histomorphometric changes in jejunal specimens. This was associated with frequent (21%-100%) and often severe in vitro jejunal disaccharidase deficiency. In vivo hydrolysis of lactose, sucrose, and palatinose was impaired in 25%-75% of patients, apart from HIV well patients, who were normal. The prevalence of the in vivo lactase and sucrase deficiency was significantly (P < 0.006) lower than in vitro and severe in about 30%.

CONCLUSIONS

Intestinal disaccharidase deficiency is common both in vitro and in vivo in HIV-seropositive patients but sufficiently severe to consider lactose withdrawal only in about a quarter of the patients with AIDS and diarrhoea.

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.

Increased lactulose/rhamnose ratio during fluid load is caused by increased urinary lactulose excretion

Noninvasive assessment of intestinal permeability in vivo is based on the measurement of urinary excretion of orally administered sugar probes. It is expressed as a ratio, usually lactulose/rhamnose or 3-O-methyl-D-glucose (3-OMG)/rhamnose. In both endotoxemic and control rats that were receiving fluid, we observed an increase in the recovery of lactulose and 3-OMG but not rhamnose in both groups, suggesting an enhancement of intestinal permeability. In the measurement of intestinal permeability, all pre- and postmucosal factors are considered equal for all sugars. We hypothesized that postmucosal factors and not changes in intestinal permeability caused the increased urinary lactulose and 3-OMG recoveries observed during fluid loading. Therefore, the effects of fluid loading on urinary excretion of the sugar probes were studied in healthy rats receiving the sugars intravenously. After intravenous injection, fluid loading increased urinary lactulose recovery threefold but not that of 3-OMG and rhamnose. In conclusion, fluid loading increases the lactulose/rhamnose ratio independent of changes in intestinal permeability. The 3-OMG/rhamnose ratio is not influenced by fluid loading.

Sugar tests detect celiac disease among first-degree relatives

OBJECTIVES

First-degree relatives of patients with celiac disease are at high risk for developing the disease themselves. Detection of serum antibodies and intestinal permeability tests have been useful to identify candidates for intestinal biopsies. Recently it was demonstrated that abnormal sucrose permeability is a very sensitive marker of active disease. Our objectives in this prospective study were (1) to assess the screening value of permeability tests, and (2) to compare the usefulness of these markers with that of the celiac disease-related serology in screening for celiac disease in a cohort of first-degree relatives of well-known patients.

METHODS

We performed sugar tests in 66 first-degree relatives of probands. Subjects ingested 450 ml of a solution containing sucrose (100 g), lactulose (5 g), and mannitol (2 g). Subsequently, a complete overnight urine collection was obtained. Measurement of sugars was performed by high-performance liquid chromatography. All relatives were evaluated for antigliadin (type IgA and IgG) and endomysial antibodies and subjects positive for any test underwent intestinal biopsy.

RESULTS

Twelve relatives were diagnosed as having small intestinal mucosal atrophy. Increased sucrose permeability was detected in 9 (75%) of these patients. Four false-positive determinations were found but all had gastric erosions, which is known to increase sucrose permeability independently of duodenal damage. Increased lactulose/mannitol ratios were observed in all new celiac patients. An additional nine relatives had positive results; however, four of them did not accept intestinal biopsy and the remaining five did not seem to have histological evidence of disease. Endomysial antibodies were detected in 11 of 12 patients and no false-positive cases were observed. Antigliadin antibodies were 75% sensitive and 88% specific.

CONCLUSIONS

Our study demonstrated that screening using the endomysial antibody test is highly sensitive and specific for detecting celiac disease; however, almost 10% can be missed. The addition of lactulose/mannitol permeability testing to the screening protocol allowed us to detect all relatives who actually presented with evidence of gluten sensitivity. Sucrose permeability exhibited a lower sensitivity; however, it did detect other endoscopically visible lesions.

Injurious effect of Helicobacter pylori culture fluid to gastroduodenal mucosa, and its detoxification by sucralfate in the rat

BACKGROUND

Helicobacter pylori plays an important role in the pathogenesis of peptic ulcer. Although several cytotoxins related to H. pylori have been reported, their effects on gastroduodenal mucosa have not been well evaluated in vivo.

AIM

To investigate the effects of the combination of acid and toxic substances derived from H. pylori on gastroduodenal mucosa, and to observe the effect of sucralfate on such factors in the rat.

METHODS

Male Sprague-Dawley rats were fasted overnight and anaesthetized. The pylorus was ligated, and a double-lumen cannula was inserted into the forestomach for gastric luminal perfusion. In other animals, a cannula was inserted to perfuse the proximal duodenum. 51Cr-EDTA was administered intravenously and mucosal integrity was monitored by measuring the blood-to-lumen 51Cr-EDTA clearance. After 72 h of culture of H. pylori (NCTC11637 and Sydney strain 1), Brucella broth containing 3% FBS was filtered to remove the bacteria (supernate of H. pylori culture fluid; HPsup). HPsup was acidified (pH=2.0) with HCl, and tested for its injurious action on gastric or duodenal mucosa by luminal perfusion. HPsup was incubated with sucralfate for 30 min. The supernate was collected by centrifugation and the pH was readjusted to 2.0. This sucralfate-treated HPsup was used to test the effect of sucralfate against H. pylori-related mucosal injurious factors.

RESULTS

Non-acidified and acidified HPsup did not cause any detectable injury to the gastric mucosa. Non-acidified HPsup did not cause injury in the duodenal mucosa. However, acidified HPsup induced a significantly greater increase in 51Cr-EDTA clearance and greater histological damage than in controls. Sucralfate completely reversed this.

CONCLUSION

These results suggest that an H. pylori-related toxic substance may aggravate duodenal acid injury by acting on luminal surfaces, and that the detoxification of this substance by sucralfate may contribute to its anti-ulcer action.

Regional differences in quinine absorption from the undisturbed human colon assessed using a timed release delivery system

PURPOSE

To investigate the regional absorption characteristics of the distal gut using two markers of permeability, quinine (a transcellular probe) and 51CrEDTA (a paracellular probe).

METHODS

The permeability markers were delivered to the undisturbed gastrointestinal tract in 39 healthy volunteers using an oral timed-release delivery vehicle which allowed pulsed release within a particular site of the gut. Site of release was identified using gamma scintigraphy. Absorption of quinine and 51CrEDTA was assessed by measuring the percent excretion in the urine using HPLC and gamma counting respectively. Serial plasma samples allowed time-concentration curves for quinine to be plotted.

RESULTS

There was a significant trend for diminished absorption with more distal delivery of the transcellular probe, quinine, which was: 6.26 +/- 0.87% (small intestine, n = 10); 4.65 +/- 0.93% (ascending colon, n = 16); and 2.59 +/- 0.52% (transverse colon, n = 10) of the ingested dose excreted respectively (p < 0.001). No such gradient was seen with the paracellular marker, 51CrEDTA.

CONCLUSIONS

These results suggest that delayed release formulations should aim for release in the distal small bowel and proximal colon if absorption is to be maximised. Absorption by the transcellular route diminishes in the more distal colon, a fact which has implications for delayed or sustained release formulations.

The sensitivity of the lactulose/rhamnose gut permeability test

BACKGROUND

The lactulose/rhamnose (L/R) intestinal permeability test is widely used. However, different quantities and proportions of lactulose and rhamnose are used. The aim of this study was to determine whether a low dosage of lactulose is able to discriminate between normal and increased permeability.

MATERIALS AND METHODS

Two groups of 10 healthy subjects were studied. In group 1, three different iso-osmolar test solutions were administered on 3 days. The solutions consisted of 10 g of L with 1 g of R, 5 g of L with 0.5 g of R and 1 g of L with 0.1 g of R in 65 mL of water. Group 2 ingested these solutions 1 h after ingestion of 750 mg of chenodeoxycholeic acid (CDCA), which is known to increase permeability. The urinary L/R ratio was determined using high-performance liquid chromatography. Data are presented as medians (range).

RESULTS

In group 1, no differences were observed between the three solutions. In Group 2, there was a significant difference (P = 0.045) between the three solutions. The L/R ratios were 0.0079 (0.0024-0.0152) (1L to 0.1R), 0.0138 (0.0066-0.0192) (5L to 0.5R) and 0.0144 (0.0074-0.0374) (10L to 1R). The L/R ratio differed significantly between Groups 1 and 2 (P < 0.001) using the 5L to 0.5R and 10L to 1R solutions respectively.

CONCLUSION

If the permeability is increased, the urinary L/R ratio depends on the quantity of lactulose and rhamnose administered in equal proportion. 5L to 0.5R is sufficient to discriminate between a normal and a moderately increased permeability.

Intestinal permeability in patients with acute myeloid leukemia

Intestinal permeability was studied in patients with acute myeloid leukemia (AML) before, during and after chemotherapy. Intestinal permeability was determined by the lactulose (La)/mannitol (Ma) absorption test in 16 adult patients with de novo AML. The hydrogen breath test was used to disclose bacterial fermentation of the test substances in the small intestine. The permeability was found significantly increased (p<0.02) in the patients before induction chemotherapy treatment. During induction treatment and throughout the cytopenic period the intestinal permeability was constantly and significantly increased, compared with controls. In patients with abnormally increased permeability, no increase in hydrogen breath test result was noted. From our results it can be concluded that increased intestinal permeability is present in AML patients before commencing chemotherapy. Factors other than chemotherapy would seem to be more important regarding the occurrence of intestinal disturbances in these patients.

Increased intestinal permeability is associated with the development of multiple organ dysfunction syndrome in critically ill ICU patients

We conducted a prospective, observational cohort study designed to compare intestinal permeability (IP) and development of multiple organ dysfunction syndrome (MODS) in a subset of critically ill patients in an intensive care unit (ICU). All patients with an expected ICU stay of 72 h or more were entered into the study, and IP was determined on a daily basis whenever possible from the urinary fractional excretion of orally administered lactulose and mannitol (LMR). Forty-seven consecutive patients were studied, and 28 developed MODS either at the time of admission or during their ICU course. These patients, as a group, had significantly worse IP at admission than did a non-MODS cohort (LnLMR: -2.10 +/- 1.10 versus -3.26 +/- 0.83). Those patients who developed MODS following admission also had a significantly greater admission IP than did the non-MODS group (-2.51 +/- 0.85). Differences in IP between cohorts could not be explained by differences in the incidence of systemic inflammatory response syndrome (SIRS)/sepsis or shock. With multivariate regression analysis, the only parameter present on admission that was predictive of subsequent MODS was IP. Differences in IP and the severity of organ dysfunction were also present (MODS severity mild: -3.01 +/- 0.72; moderate: -1.97 +/- 0.69; and severe: -1.12 +/- 0.96). Patients who developed MODS had a persistently abnormal IP during their ICU stay, and a significantly delayed improvement in their IP compared with the non-MODS cohort. We conclude that the development of MODS is associated with an abnormal and severe derangement of IP that is detectable prior to the onset of the syndrome. This observation lends credence to the premise that gastrointestinal (GI) dysfunction may be causally associated with the development of MODS in the critically ill patient.

Intestinal epithelial hyperpermeability. Mechanisms and relevance to disease

Pathologic increases in intestinal permeability to hydrophilic macromolecules has been identified in a number of clinical conditions. The significance of gut barrier dysfunction as a clinical issue remains to be delineated, although it seems likely that alterations in intestinal epithelial permeability play a causative role in a number of conditions ranging from inflammatory bowel disease to the development of complications after cardiopulmonary bypass. It is unlikely that any one mechanism can account for all cases of intestinal hyperpermeability. Rather, it is more probable that myriad factors or combinations of factors, including mesenteric ischemia and cytokine-induced phenomena, lead to alterations in permeability in different clinical entities. Nevertheless, from a purely mechanistic standpoint, some common themes, notably the role of ATP depletion, increases in [Ca2+]i, and cytoskeletal derangements in enterocytes, have emerged as being particularly important.

Intestinal permeability in cystic fibrosis in relation to genotype

BACKGROUND

The purpose of this study was to investigate whether the increase intestinal permeability (IP) seen in patients with cystic fibrosis (CF) is correlated with the basic defect, as revealed by the patient's genotype, and/or whether the intestinal disturbance reflects secondary abnormalities such as essential fatty acid deficiency.

METHODS

Nineteen CF patients were compared with nine age- and sex-matched healthy controls. IP was evaluated by studying urinary excretion for 5 hours after a test meal containing lactulose, L-rhamnose and xylose in water. Urine was analyzed for carbohydrates, and blood samples were taken for determination of the fatty acid pattern of serum phospholipids. The CF patients were grouped according to genotype: homozygous for delta F508, heterozygous for alpha F508, or unidentified.

RESULTS

Patients who were homozygous (n = 9) or heterzygous (n = 6) for delta F508 had significantly higher lactulose/L-rhamnose excretion ratios (mean(range) values of 0.08(0.05-0.13) and 0.09(0.03-0.13), respectively) than patients (n = 4) with unidentified genotypes [0.03(0.02-0.05); p = 0.005] or healthy controls [0.02(0.003-0.06); p = 0.002]. CF patients with EFAD (n = 6) did not differ from those with a normal pattern of serum phospholipid fatty acids, the lactulose/L-rhamnose excretion ratio being 0.08(0.02-0.13) and 0.07(0.03-0.12), respectively.

CONCLUSIONS

These data show that the IP in CF was related to patient genotype; those homozygozous or heterozygous for delta F508 having a significantly increased IP compared with patients with unidentified genotypes, who had IP values within the normal range.

Luminal bacteria and small-intestinal permeability

BACKGROUND

The influence of luminal bacteria on small-intestinal permeability has not been fully assessed. This study addressed this issue.

METHODS

Thirty-four subjects (mean age 64 years; range 22-95 years) were investigated for possible small-intestinal bacterial overgrowth (SIBO) with culture of a small-intestinal aspirate. A lactulose/mannitol small-intestinal permeability test was performed, small-intestinal histology assessed and serum vitamin B12 concentrations measured in all subjects. Permeability was also assessed in a control group of 34 asymptomatic volunteers.

RESULTS

Urinary lactulose/mannitol ratios were significantly increased in subjects with SIBO with colonic-type flora (P < 0.0005), even in the absence of villous atrophy. Urinary lactulose/mannitol ratios were increased in this group due to significantly increased urinary lactulose concentrations (P < 0.0005) rather than reduced urinary mannitol levels, after correcting for inter-subject variations in renal function. Counts of intraepithelial lymphocytes of CD8 phenotype were significantly increased in this group (P = 0.003). Although a significant correlation was found between intraepithelial lymphocyte counts and small-intestinal permeability overall (P < 0.002), these counts were not significantly different in subjects with SIBO with colonic-type flora whose permeability values were < or = > 0.028, the upper limit of normal in asymptomatic controls. Serum vitamin B12 concentrations did not differ significantly between groups (P > 0.5). Ageing did not independently influence small-intestinal permeability (P > 0.5).

CONCLUSIONS

Small-intestinal permeability is increased in subjects with SIBO with colonic-type bacteria. This effect is independent of ageing and not mediated by vitamin B12 deficiency. Although counts of intraepithelial lymphocytes of CD8 phenotype are increased in this disorder, it is also unlikely that these cells play an important causative role in this process. Routine light microscopic assessment underestimates the prevalence of small-intestinal functional disturbance in this disorder.

Detection of naproxen-induced intestinal permeability change may be facilitated by adding a standardized meal but not by forming marker ratios

BACKGROUND

We recently compared the intestinal permeability markers polysucrose (PS) 15,000, 51Cr-ethylenediaminetetraacetic acid (EDTA), and 14C-mannitol in healthy humans. We have now studied the ability of these markers to show non-steroidal anti-inflammatory drug (NSAID)-induced intestinal damage, with special regard to the possibility of improving discrimination versus healthy intestine by using a hyperosmolar test solution, adding a standardized liquid meal, calculating paracellular/ transcellular marker excretion ratios, or correcting excretion values for urinary volume.

METHODS

Seventeen healthy volunteers ingested a solution containing PS 15,000, 51Cr-EDTA, and 14C-mannitol before and after 1 week of naproxen intake, the solution being isosmolar, hyperosmolar, or isosmolar and followed by a standardized liquid meal. Fractional urinary excretion of the substances was measured over 0-4 h, 4-8 h, and 8-12 h.

RESULTS

The excretion of the paracellular permeability markers PS 15,000 and 51Cr-EDTA increased after NSAID pretreatment, whereas that of the transcellular marker 14C-mannitol was unaffected. A standardized liquid meal reduced test variability for all markers and tended to improve differentiation between diseased and healthy intestine. A hyperosmolar test solution tended to improve differentiation for 51Cr-EDTA but not for PS 15,000. Calculating a paracellular/transcellular ratio or correcting excretion values for urinary volume did not improve the differentiation.

CONCLUSIONS

A standardized liquid meal may improve the capacity of permeability tests to distinguish between healthy and NSAID-damaged intestine.