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

Breaking the Barrier: The Role of Gut Epithelial Permeability in the Pathogenesis of Hypertension

PURPOSE OF THE REVIEW

To review what intestinal permeability is and how it is measured, and to summarise the current evidence linking altered intestinal permeability with the development of hypertension.

RECENT FINDINGS

Increased gastrointestinal permeability, directly measured in vivo, has been demonstrated in experimental and genetic animal models of hypertension. This is consistent with the passage of microbial substances to the systemic circulation and the activation of inflammatory pathways. Evidence for increased gut permeability in human hypertension has been reliant of a handful of blood biomarkers, with no studies directly measuring gut permeability in hypertensive cohorts. There is emerging literature that some of these putative biomarkers may not accurately reflect permeability of the gastrointestinal tract. Data from animal models of hypertension support they have increased gut permeability; however, there is a dearth of conclusive evidence in humans. Future studies are needed that directly measure intestinal permeability in people with hypertension.

Development and application of a multi-sugar assay to assess intestinal permeability

Aim: Bioanalytical assays to measure rhamnose, erythritol, lactulose and sucralose in human urine and plasma were developed to support an indomethacin challenge study for intestinal permeability assessment in healthy participants. Methods: The multi-sugar assays utilized 5-μl sample matrix and a simple chemical derivatization with acetic anhydride, followed by RPLC-MS/MS detection. Results: Rhamnose and erythritol quantification was established between 1.00-1,000 μg/ml in urine and 250-250,000 ng/ml in plasma. For lactulose and sucralose, dynamic ranges of 0.1-100 μg/ml (urine) and 25-25,000 ng/ml (plasma) were applied for biological measurements. Conclusion: This work helped overcome some of the common analytical challenges associated with the bioanalysis of mono- and disaccharides and achieved improved limits of quantification.

Associations between various markers of intestinal barrier and immune function after a high-intensity exercise challenge

Strenuous exercise can result in disruption of intestinal barrier function and occurrence of gastrointestinal symptoms. The aim of this exploratory study was to elucidate systemic effects of increased intestinal permeability after high-intensity exercise. Forty-one endurance-trained subjects performed a 60-min treadmill run at 80% VO2max. Small intestinal permeability was measured as urinary excretion ratio of lactulose/rhamnose (L/R). Blood, saliva and feces were analyzed for gut barrier and immune-related biomarkers. The exercise challenge increased several markers of intestinal barrier disruption, immune function and oxidative stress. We found a negative correlation between L/R ratio and uric acid (r = -0.480), as well as a positive correlation between the L/R ratio and fecal chromogranin A in male participants (r = 0.555). No significant correlations were found between any of the markers and gastrointestinal symptoms, however, perceived exertion correlated with the combination of IL-6, IL-10 and salivary cortisol (r = 0.492). The lack of correlation between intestinal permeability and gastrointestinal symptoms could be due to minor symptoms experienced in lab settings compared to real-life competitions. The correlation between L/R ratio and uric acid might imply a barrier-protective effect of uric acid, and inflammatory processes due to strenuous exercise seem to play an important role regarding physical exhaustion.

Intestinal Barrier Dysfunction and Gut Microbiota in Non-Alcoholic Fatty Liver Disease: Assessment, Mechanisms, and Therapeutic Considerations

Non-alcoholic fatty liver disease (NAFLD) is a type of metabolic stress liver injury closely related to insulin resistance (IR) and genetic susceptibility without alcohol consumption, which encompasses a spectrum of liver disorders ranging from simple hepatic lipid accumulation, known as steatosis, to the more severe form of steatohepatitis (NASH). NASH can progress to cirrhosis and hepatocellular carcinoma (HCC), posing significant health risks. As a multisystem disease, NAFLD is closely associated with systemic insulin resistance, central obesity, and metabolic disorders, which contribute to its pathogenesis and the development of extrahepatic complications, such as cardiovascular disease (CVD), type 2 diabetes mellitus, chronic kidney disease, and certain extrahepatic cancers. Recent evidence highlights the indispensable roles of intestinal barrier dysfunction and gut microbiota in the onset and progression of NAFLD/NASH. This review provides a comprehensive insight into the role of intestinal barrier dysfunction and gut microbiota in NAFLD, including intestinal barrier function and assessment, inflammatory factors, TLR4 signaling, and the gut-liver axis. Finally, we conclude with a discussion on the potential therapeutic strategies targeting gut permeability and gut microbiota in individuals with NAFLD/NASH, such as interventions with medications/probiotics, fecal transplantation (FMT), and modifications in lifestyle, including exercise and diet.

Re-evaluation of erythritol (E 968) as a food additive

This opinion addresses the re-evaluation of erythritol (E 968) as food additive and an application for its exemption from the laxative warning label requirement as established under Regulation (EU) No 1169/2011. Erythritol is a polyol obtained by fermentation with Moniliella pollinis BC or Moniliella megachiliensis KW3-6, followed by purifications and drying. Erythritol is readily and dose-dependently absorbed in humans and can be metabolised to erythronate to a small extent. Erythritol is then excreted unchanged in the urine. It does not raise concerns regarding genotoxicity. The dataset evaluated consisted of human interventional studies. The Panel considered that erythritol has the potential to cause diarrhoea in humans, which was considered adverse because its potential association with electrolyte and water imbalance. The lower bound of the range of no observed adverse effect levels (NOAELs) for diarrhoea of 0.5 g/kg body weight (bw) was identified as reference point. The Panel considered appropriate to set a numerical acceptable daily intake (ADI) at the level of the reference point. An ADI of 0.5 g/kg bw per day was considered by the Panel to be protective for the immediate laxative effect as well as potential chronic effects, secondary to diarrhoea. The highest mean and 95th percentile chronic exposure was in children (742 mg/kg bw per day) and adolescents (1532 mg/kg bw per day). Acute exposure was maximally 3531 mg/kg bw per meal for children at the 99th percentile. Overall, the Panel considered both dietary exposure assessments an overestimation. The Panel concluded that the exposure estimates for both acute and chronic dietary exposure to erythritol (E 968) were above the ADI, indicating that individuals with high intake may be at risk of experiencing adverse effects after single and repeated exposure. Concerning the new application, the Panel concluded that the available data do not support the proposal for exemption.

Gastrointestinal cell injury and perceived symptoms after running the Boston Marathon

Gastrointestinal (GI) disturbances are a prevalent cause of marathon related complaints, and in extreme cases can promote life-threatening conditions such as exertional heat stroke. Our aim was to study intestinal cell injury [via intestinal fatty acid binding protein (I-FABP)] and perceived GI distress symptoms among marathon runners. We also examined potential risk factors (e.g., inadequate sleep) that could exacerbate GI disturbances in healthy, trained endurance runners. This was a parallel mixed-methods study design. 2019 Boston Marathon participants were recruited via email and subjects completed surveys before the race describing demographics and training history. Participants completed a GI questionnaire to assess presence and severity of symptoms, a survey regarding risk factors (e.g., recent illness, medications) that could promote GI disturbances, and provided a urine sample at three time points (immediately pre-race, post-race, and 24-h post-race). Due to weather, blood samples were only collected immediately and 24-h post-race. A total of 40 runners (males: n = 19, age = 44.9 ± 10.8 years; females: n = 21, age = 44.8 ± 10.6 years) completed this study. I-FABP significantly decreased from post-race (3367.5 ± 2633.5 pg/mL) to 24-h post-race (1657.3 ± 950.7 pg/mL, t (39) = -4.228, p < .001, d = -.669). There was a significant difference in overall GI symptom scores across the three time points (F (2, 39) = 41.37, p < .001). The highest average score occurred post-race (.84 ± .68), compared to pre-race (.09 ± .12) and 24-h post-race (.44 ± .28). Post-race I-FABP (r = .31, p = .048) and post-race urine specific gravity (r = .33, p = .041) were significantly correlated with post-race GI symptom scores. Our study provides further support to the individualized nature of GI disturbances, with participants experiencing a wide range of risk factors that can influence the extent of GI damage and perceived symptoms during and after exercise.

Evaluating and comparing tolerance, nutritional quality and bio-functional activity of bovine-plasma, corn and whey proteins, outcomes of a randomized double blind controlled trial

Important considerations in the choice of future sustainable protein sources for human application are tolerance, nutritional quality, and potential health benefits. We evaluated, in a double-blind cross-over intervention trial, tolerance, nutritional quality, and potential health effects of two sustainable protein sources. Thirty-six apparently healthy older adults (age 62.3 ± 7.2yrs, BMI 25 ± 3 kg/m2) received 40 g/day bovine-plasma protein (BP), corn protein (CP) or, as a benchmark, whey protein (WP) for one week with a washout period of one week in-between. In 12 participants, we also determined postprandial amino acid (PAA) uptake kinetics upon consumption of 20 g BP, CP, or WP. Changes in self-reported gastrointestinal complaints and intestinal permeability assessed using a multi-sugar acetylsalicylic acid test did not differ between the interventions. Clear differences in PAA responses were observed after consumption of the different proteins, but clear essential amino acid responses were observed for all proteins. BP consumption resulted in a small but significant increase in blood pressure outcomes, and CP consumption resulted in a small but significant decrease in insulin levels when compared to the other interventions. In conclusion, alternative protein concentrates and isolates studied here can be consumed in relative high quantities without experiencing unwanted GI complaints or gut barrier dysfunction and they can be a good source of essential amino acids. The rise in blood pressure observed during the BP intervention, potentially linked to the elevated salt content of the BP, constitutes a potential health issue. Future studies with longer intervention periods might however be recommended.

Serotonin reuptake transporter deficiency promotes liver steatosis and impairs intestinal barrier function in obese mice fed a Western-style diet

BACKGROUND

Intestinal barrier dysfunctions have been associated with liver steatosis and metabolic diseases. Besides nutritional factors, like a Western-style diet (WSD), serotonin has been linked with leaky gut. Therefore, we aimed to evaluate the role of serotonin in the pathogenesis of intestinal barrier dysfunctions and liver steatosis in mice fed high-fat and high-sugar diets.

METHODS

6-8 weeks old male serotonin reuptake transporter knockout mice (SERT-/- ) and wild-type controls (SERT+/+ ) were fed either a WSD or a control diet (CD) ad libitum with or without fructose 30% (F) added to the drinking water for 12 weeks. Markers of liver steatosis and intestinal barrier function were assessed.

KEY RESULTS

SERT-/- mice showed increased weight gain compared with SERT+/+ mice when fed a WSD ± F for 12 weeks (p < 0.05), whereby SERT-/- mice exhibited reduced energy (-21%) intake. Furthermore, SERT knockout resulted in a more pronounced liver steatosis (p < 0.05), enhanced levels of endotoxin in portal vein plasma (p < 0.05), and increased liver expression of Tnf and Myd88 (p < 0.05), when mice were fed a WSD ± F. Finally, SERT-/- mice, when compared with SERT+/+ mice, had a decreased mRNA expression of Muc2 (p < 0.01), Ocln (p < 0.05), Cldn5 (p = 0.054) and 7 (p < 0.01), Defa5 (p < 0.05) and other antimicrobial peptides in the ileum. On the protein level, ZO-1 (p < 0.01) and DEFA5 protein (p < 0.0001) were decreased.

CONCLUSION AND INFERENCES

Our data demonstrate that SERT knockout causes weight gain, liver steatosis, and leaky gut, especially in mice fed a WSD. Therefore, SERT induction could be a novel therapeutic approach to improve metabolic diseases associated with intestinal barrier dysfunction.

Intestinal permeability in patients with IgA nephropathy and other glomerular diseases: an observational study

BACKGROUND

A dysregulated 'gut-kidney axis' may contribute to immunoglobulin A nephropathy (IgAN). We studied whether IgAN patients have disturbed intestinal permeability.

METHODS

In a prospective, cross sectional, pilot study we assessed intestinal permeability in 35 IgAN patients, 18 patients with non-IgAN glomerulonephritides (GNs) and 19 healthy controls. After an overnight fast, trial participants ingested a multi-sugar solution and samples were obtained from 0 to 2, 2 to 5- and 5 to 24-h urine portions. Urinary sugar concentrations were quantified using isocratic ion-exchange high performance liquid chromatography. Indices of small intestinal permeability (0-2-h lactulose/L-rhamnose (L/R) ratio), distal small intestinal and proximal colonic permeability (2-5-h sucralose/erythritol (S/E) ratio) and colonic permeability (5-24-h sucralose/erythritol (S/E) ratio) were evaluated. Associations between groups and indices of intestinal permeability were investigated by a linear mixed model.

RESULTS

Small intestinal permeability (0-2 h L/R-ratio) was significantly increased in patients with glomerular diseases versus healthy controls. More precisely, increased small intestinal permeability was exclusively noted in non-IgAN GN patients, whereas IgAN patients exhibited a trend towards elevated small intestinal permeability. In total, 54% of patients with IgAN and 67% of non-IgAN GN patients had increased small intestinal permeability. Neither distal small intestinal and proximal colonic permeability nor colonic gut permeability indices (i.e., 2-5 h and 5-24 h S/E ratios) were significantly different between controls and any of the GN patient groups.

CONCLUSION

The present single center pilot study suggests that disturbed intestinal permeability is common in patients with glomerular diseases and is not specific for IgAN.

TRIAL REGISTRATION NUMBER

German Clinical Trials Register DRKS00021533, Date: 24.04.2020.

Ibuprofen Increases Markers of Intestinal Barrier Injury But Suppresses Inflammation at Rest and After Exercise in Hypoxia

PURPOSE

The purpose of this study was to evaluate the effects of acute ibuprofen consumption (2 × 600-mg doses) on markers of enterocyte injury, intestinal barrier dysfunction, inflammation, and symptoms of gastrointestinal (GI) distress at rest and after exercise in hypobaric hypoxia.

METHODS

Using a randomized double-blind placebo-controlled crossover design, nine men (age, 28 ± 3 yr; weight, 75.4 ± 10.5 kg; height, 175 ± 7 cm; body fat, 12.9% ± 5%; V̇O 2 peak at 440 torr, 3.11 ± 0.65 L·min -1 ) completed a total of three visits including baseline testing and two experimental trials (placebo and ibuprofen) in a hypobaric chamber simulating an altitude of 4300 m. Preexercise and postexercise blood samples were assayed for intestinal fatty acid binding protein (I-FABP), ileal bile acid binding protein, soluble cluster of differentiation 14, lipopolysaccharide binding protein, monocyte chemoattractant protein-1, tumor necrosis factor α (TNF-α), interleukin-1β, and interleukin-10. Intestinal permeability was assessed using a dual sugar absorption test (urine lactulose-to-rhamnose ratio).

RESULTS

Resting I-FABP (906 ± 395 vs 1168 ± 581 pg·mL -1 ; P = 0.008) and soluble cluster of differentiation 14 (1512 ± 297 vs 1642 ± 313 ng·mL -1 ; P = 0.014) were elevated in the ibuprofen trial. Likewise, the urine lactulose-to-rhamnose ratio (0.217 vs 0.295; P = 0.047) and the preexercise to postexercise change in I-FABP (277 ± 308 vs 498 ± 479 pg·mL -1 ; P = 0.021) were greater in the ibuprofen trial. Participants also reported greater upper GI symptoms in the ibuprofen trial ( P = 0.031). However, monocyte chemoattractant protein-1 ( P = 0.007) and TNF-α ( P = 0.047) were lower throughout the ibuprofen trial compared with placebo (main effect of condition).

CONCLUSIONS

These data demonstrate that acute ibuprofen ingestion aggravates markers of enterocyte injury and intestinal barrier dysfunction at rest and after exercise in hypoxia. However, ibuprofen seems to suppress circulating markers of inflammation.

Potential Modulation of Inflammation by Probiotic and Omega-3 Supplementation in Elderly with Chronic Low-Grade Inflammation—A Randomized, Placebo-Controlled Trial

Probiotic and omega-3 supplements have been shown to reduce inflammation, and dual supplementation may have synergistic health effects. We investigated if the novel combination of a multi-strain probiotic (containing B. lactis Bi-07, L. paracasei Lpc-37, L. acidophilus NCFM, and B. lactis Bl-04) alongside omega-3 supplements reduces low-grade inflammation as measured by high-sensitivity C-reactive protein (hs-CRP) in elderly participants in a proof-of-concept, randomized, placebo-controlled, parallel study (NCT04126330). In this case, 76 community-dwelling elderly participants (median: 71.0 years; IQR: 68.0–73.8) underwent an intervention with the dual supplement (n = 37) or placebo (n = 39) for eight weeks. In addition to hs-CRP, cytokine levels and intestinal permeability were also assessed at baseline and after the eight-week intervention. No significant difference was seen for hs-CRP between the dual supplement group and placebo. However, interestingly, supplementation did result in significant increases in the level of the anti-inflammatory marker IL-10. In addition, dual supplementation increased levels of valeric acid, further suggesting the potential of the supplements in reducing inflammation and conferring health benefits. Together, the results suggest that probiotic and omega-3 dual supplementation exerts modest effects on inflammation and may have potential use as a non-pharmacological treatment for low-grade inflammation in the elderly.

Plasma Metabolic and Lipidomic Fingerprinting of Individuals with Increased Intestinal Permeability

The dual-sugar intestinal permeability test is a commonly used test to assess changes in gut barrier function. However, it does not identify functional changes and the exact mechanism of damage caused by the increased intestinal permeability. This study aims to explore the application of untargeted metabolomics and lipidomics to identify markers of increased intestinal permeability. Fifty fasting male participants (18–50 years) attended a single visit to conduct the following procedures: assessment of anthropometric measures, assessment of gastrointestinal symptoms, intestinal permeability test, and assessment of blood samples 90 min post-administration of the intestinal permeability test. Rhamnose and lactulose were analysed using gas chromatography-mass spectrometry (GC-MS). Untargeted polar metabolites and lipidomics were assessed by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF MS). There was an elevated lactulose/rhamnose ratio in 27 subjects, indicating increased permeability compared to the remaining 23 control subjects. There were no significant differences between groups in characteristics such as age, body mass index (BMI), weight, height, and waist conference. Fourteen metabolites from the targeted metabolomics data were identified as statistically significant in the plasma samples from intestinal permeability subjects. The untargeted metabolomics and lipidomics analyses yielded fifteen and fifty-one statistically significant features, respectively. Individuals with slightly elevated intestinal permeability had altered energy, nucleotide, and amino acid metabolism, in addition to increased glutamine levels. Whether these biomarkers may be used to predict the early onset of leaky gut warrants further investigation.

Intestinal permeability before and after albendazole treatment in low and high socioeconomic status schoolchildren in Makassar, Indonesia

Intestinal helminths are highly prevalent in low-SES children and could contribute to poor health outcomes either directly or via alteration of the gut microbiome and gut barrier function. We analysed parasitic infections and gut microbiota composition in 325 children attending high- and low-SES schools in Makassar, Indonesia before and after albendazole treatment. Lactulose/Mannitol Ratio (LMR, a marker of gut permeability); I-FABP (a surrogate marker of intestinal damage) as well as inflammatory markers (LBP) were measured. Helminth infections were highly prevalent (65.6%) in low-SES children. LMR and I-FABP levels were higher in low-SES children (geomean (95%CI): 4.03 (3.67-4.42) vs. 3.22 (2.91-3.57); p. adj < 0.001; and 1.57 (1.42-1.74) vs. 1.25 (1.13-1.38); p. adj = 0.02, respectively) while LBP levels were lower compared to the high-SES (19.39 (17.09-22.01) vs. 22.74 (20.07-26.12); p.adj = 0.01). Albendazole reduced helminth infections in low-SES and also decreased LMR with 11% reduction but only in helminth-uninfected children (estimated treatment effect: 0.89; p.adj = 0.01). Following treatment, I-FABP decreased in high- (0.91, p.adj < 0.001) but increased (1.12, p.adj = 0.004) in low-SES children. Albendazole did not alter the levels of LBP. Microbiota analysis showed no contribution from specific bacterial-taxa to the changes observed. Intestinal permeability and epithelial damage are higher while peripheral blood inflammatory marker is lower in children of low-SES in Indonesia. Furthermore, treatment decreased LMR in helminth-uninfected only.

Mediterranean Diet Adherence in People With Parkinson's Disease Reduces Constipation Symptoms and Changes Fecal Microbiota After a 5-Week Single-Arm Pilot Study

Introduction: Non-motor symptoms of Parkinson's disease (PD) such as gastrointestinal (GI) dysfunction are common, yet little is known about how modifying dietary intake impacts PD symptoms. The aim of this study in individuals with PD was to determine whether a Mediterranean diet intervention is feasible and affects GI function, intestinal permeability and fecal microbial communities.

Methods: A single-arm, 5-week Mediterranean diet intervention study was conducted in eight people with PD. Daily and weekly questionnaires were administered to determine changes in GI symptoms. Urine and stool samples were collected at baseline and after 5 weeks to assess intestinal permeability and fecal microbial communities. Additionally, live-in partners of the participants with PD were matched as controls (n = 8) for baseline urine and stool samples.

Results: Participants with PD increased intake of Mediterranean diet based on adherence scores from baseline to week 5 (4.4 ± 0.6 vs. 11.9 ± 0.7; P < 0.01 with >10 representing good adherence), which was linked with weight loss (77.4 kg vs. 74.9 kg, P = 0.01). Constipation syndrome scores decreased after 5 weeks (2.3 ± 0.5 vs. 1.5 ± 0.3; P = 0.04). Bilophila, was higher at baseline in PD (0.6 ± 0.1% vs. 0.2 ± 0.1% P = 0.02) and slightly decreased after the diet intervention (0.5 ± 0.1%; P = 0.01). Interestingly, the proportion of Roseburia was significantly lower in PD compared to controls (0.6 ± 0.2% vs. 1.6 ± 0.3%; P = 0.02) and increased at week 5 (0.9 ± 0.2%; P < 0.01). No differences were observed for markers of intestinal permeability between the control and PD groups or post-intervention.

Conclusions: Short-term Mediterranean diet adherence is feasible in participants with PD; correlated with weight loss, improved constipation, and modified gut microbiota.

Clinical Trial Registration:ClinicalTrials.gov, identifier: NCT03851861.

Sauna dehydration as a new physiological challenge model for intestinal barrier function

The intestinal barrier plays a crucial role in maintaining gut health, and an increased permeability has been linked to several intestinal and extra-intestinal disorders. There is an increasing demand for interventions aimed at strengthening this barrier and for in vivo challenge models to assess their efficiency. This study investigated the effect of sauna-induced dehydration on intestinal barrier function (clinicaltrials.gov: NCT03620825). Twenty healthy subjects underwent three conditions in random order: (1) Sauna dehydration (loss of 3% body weight), (2) non-steroidal anti-inflammatory drug (NSAID) intake, (3) negative control. Intestinal permeability was assessed by a multi-sugar urinary recovery test, while intestinal damage, bacterial translocation and cytokines were assessed by plasma markers. The sauna dehydration protocol resulted in an increase in gastroduodenal and small intestinal permeability. Presumably, this increase occurred without substantial damage to the enterocytes as plasma intestinal fatty acid-binding protein (I-FABP) and liver fatty acid-binding protein (L-FABP) were not affected. In addition, we observed significant increases in levels of lipopolysaccharide-binding protein (LBP), IL-6 and IL-8, while sCD14, IL-10, IFN-ɣ and TNF-α were not affected. These results suggest that sauna dehydration increased intestinal permeability and could be applied as a new physiological in vivo challenge model for intestinal barrier function.

Use of a sensitive multisugar test for measuring segmental intestinal permeability in critically ill, mechanically ventilated adults: A pilot study

BACKGROUND

Increased intestinal permeability (IP) is associated with sepsis in the intensive care unit (ICU). This study aimed to pilot a sensitive multisugar test to measure IP in the nonfasted state.

METHODS

Critically ill, mechanically ventilated adults were recruited from 2 ICUs in Australia. Measurements were completed within 3 days of admission using a multisugar test measuring gastroduodenal (sucrose recovery), small-bowel (lactulose-rhamnose [L-R] and lactulose-mannitol [L-M] ratios), and whole-gut permeability (sucralose-erythritol ratio) in 24-hour urine samples. Urinary sugar concentrations were compared at baseline and after sugar ingestion, and IP sugar recoveries and ratios were explored in relation to known confounders, including renal function.

RESULTS

Twenty-one critically ill patients (12 males; median, 57 years) participated. Group median concentrations of all sugars were higher following sugar administration; however, sucrose and mannitol increases were not statistically significant. Within individual patients, sucrose and mannitol concentrations were higher in baseline than after sugar ingestion in 9 (43%) and 4 (19%) patients, respectively. Patients with impaired (n = 9) vs normal (n = 12) renal function had a higher L-R ratio (median, 0.130 vs 0.047; P = .003), lower rhamnose recovery (median, 15% vs 24%; P = .007), and no difference in lactulose recovery.

CONCLUSION

Small-bowel and whole-gut permeability measurements are possible to complete in the nonfasted state, whereas gastroduodenal permeability could not be measured reliably. For small-bowel IP measurements, the L-R ratio is preferred over the L-M ratio. Alterations in renal function may reduce the reliability of the multisugar IP test, warranting further exploration.

The Effects of Exercise on Indirect Markers of Gut Damage and Permeability: A Systematic Review and Meta-analysis

AIM

Exercise appears to cause damage to the endothelial lining of the human gastrointestinal tract and elicit a significant increase in gut permeability.

OBJECTIVE

The aim of this review was to determine the effect of an acute bout of exercise on gut damage and permeability outcomes in healthy populations using a meta-analysis.

METHODS

PubMed, The Cochrane Library as well as MEDLINE, SPORTDiscus and CINHAL, via EBSCOhost were searched through February 2019. Studies were selected that evaluated urinary (ratio of disaccharide/monosaccharide excretion) or plasma markers [intestinal Fatty Acid Binding Protein (i-FABP)] of gut permeability and gut cell damage in response to a single bout of exercise.

RESULTS

A total of 34 studies were included. A random-effects meta-analysis was performed, and showed a large and moderate effect size for markers of gut damage (i-FABP) (ES 0.81; 95% CI 0.63-0.98; n = 26; p < 0.001) and gut permeability (Disaccharide Sugar/Monosaccharide Sugar) (ES 0.70; 95% CI 0.29-1.11; n = 17; p < 0.001), respectively. Exercise performed in hot conditions (> 23 °C) further increased markers of gut damage compared with thermoneutral conditions [ES 1.06 (95% CI 0.88-1.23) vs. 0.66 (95% CI 0.43-0.89); p < 0.001]. Exercise duration did not have any significant effect on gut damage or permeability outcomes.

CONCLUSIONS

These findings demonstrate that a single bout of exercise increases gut damage and gut permeability in healthy participants, with gut damage being exacerbated in hot environments. Further investigation into nutritional strategies to minimise gut damage and permeability after exercise is required. PROSPERO database number (CRD42018086339).

C, Holst JJ, Zoetendal EG, Smidt H, Troost F, Schaap FG, Damink SO, Jocken JWE, Lenaerts K, Masclee AAM, Blaak EE. Effect of wheat bran derived prebiotic supplementation on gastrointestinal transit, gut microbiota, and metabolic health: a randomized controlled trial in healthy adults with a slow gut transit

Acute intake of the wheat bran extract Arabinoxylan-Oligosaccharide (AXOS) modulates the gut microbiota, improves stool characteristics and postprandial glycemia in healthy humans. Yet, little is known on how long-term AXOS intake influences gastrointestinal (GI) functioning, gut microbiota, and metabolic health. In this randomized, placebo-controlled, double-blind study, we evaluated the effects of AXOS intake on GI function and metabolic health in adults with slow GI transit without constipation. Forty-eight normoglycemic adults were included with whole-gut transit time (WGTT) of >35 h receiving either 15 g/day AXOS or placebo (maltodextrin) for 12-wks. The primary outcome was WGTT, and secondary outcomes included stool parameters, gut permeability, short-chain fatty acids (SCFA), microbiota composition, energy expenditure, substrate oxidation, glucose, insulin, lipids, gut hormones, and adipose tissue (AT) function. WGTT was unchanged, but stool consistency softened after AXOS. 12-wks of AXOS intake significantly changed the microbiota by increasing Bifidobacterium and decreasing microbial alpha-diversity. With a good classification accuracy, overall microbiota composition classified responders with decreased WGTT after AXOS. The incretin hormone Glucagon-like protein 1 was reduced after AXOS compared to placebo. Energy expenditure, plasma metabolites, AT parameters, SCFA, and gut permeability were unchanged. In conclusion, intake of wheat bran extract increases fecal Bifidobacterium and softens stool consistency without major effects on energy metabolism in healthy humans with a slow GI transit. We show that overall gut microbiota classified responders with decreased WGTT after AXOS highlighting that GI transit and change thereof were associated with gut microbiota independent of Bifidobacterium. NCT02491125.

Intestinal function is impaired in patients with Chronic Obstructive Pulmonary Disease

BACKGROUND & AIMS

Gastrointestinal symptoms are prevalent extrapulmonary systemic manifestations of Chronic Obstructive Pulmonary Disease (COPD), but have been rarely studied. We dissected the perturbations in intestinal function in human patients with COPD using comprehensive metabolic and physiological approaches.

METHODS

In this observational study, small intestinal membrane integrity and active carrier-mediated glucose transport were quantified by sugar permeability test in 21 clinically stable patients with moderate to severe COPD (mean FEV₁, 41.2 (3.2) % of predicted) and 16 healthy control subjects. Protein digestion and absorption was analyzed using stable tracer kinetic methods. Plasma acetate, propionate, and butyrate concentrations were measured as markers of intestinal microbial metabolism.

RESULTS

Compared with healthy controls, non carrier-mediated permeability was higher (0.062 (95% CI [0.046, 0.078]) vs. 0.037 (95% CI [0.029, 0.045]), P = 0.009) and active glucose transport lower in COPD (31.4 (95% CI [23.4, 39.4])% vs. 48.0 (95% CI [37.8, 58.3])%, P = 0.010). Protein digestion and absorption was lower in COPD (0.647 (95% CI [0.588, 0.705]) vs. 0.823 (95% CI [0.737, 0.909]), P = 0007), and impairment greater in patients with dyspnea (P = 0.038), exacerbations in preceding year (P = 0.052), and reduced transcutaneous oxygen saturation (P = 0.051), and was associated with reduced physical activity score (P = 0.016) and lower quality of life (P = 0.0007). Plasma acetate concentration was reduced in COPD (41.54 (95% CI [35.17, 47.91]) vs. 80.44 (95% CI [54.59, 106.30]) μmol/L, P = 0.001) suggesting perturbed intestinal microbial metabolism.

CONCLUSIONS

We conclude that intestinal dysfunction is present in COPD, worsens with increasing disease severity, and is associated with reduced quality of life.

Alleviation of Metabolic Endotoxemia by Milk Fat Globule Membrane: Rationale, Design, and Methods of a Double-Blind, Randomized, Controlled, Crossover Dietary Intervention in Adults with Metabolic Syndrome

BACKGROUND

Milk fat globule membrane (MFGM) is a phospholipid-rich component of dairy fat that might explain the benefits of full-fat dairy products on cardiometabolic risk. Preclinical studies support that MFGM decreases gut permeability, which could attenuate gut-derived endotoxin translocation and consequent inflammatory responses that impair cardiometabolic health.

OBJECTIVES

To describe the rationale, study design, and planned outcomes that will evaluate the efficacy of MFGM-enriched milk compared with a comparator beverage on health-promoting gut barrier functions in persons with metabolic syndrome (MetS).

METHODS

We plan a double-blind, randomized, crossover trial in which people with MetS will receive a rigorously controlled eucaloric diet for 2 wk that contains 3 daily servings of an MFGM-enriched bovine milk beverage or a comparator beverage that is formulated with nonfat dairy powder, coconut and palm oils, and soy phospholipids. Compliance will be monitored by assessing urinary para-aminobenzoic acid that is added to all test beverages. After the intervention, participants will ingest a high-fat/high-carbohydrate meal challenge to assess metabolic excursions at 30-min intervals for 3 h. Nondigestible sugar probes also will be ingested prior to collecting 24-h urine to assess region-specific gut permeability. Intervention efficacy will be determined based on circulating endotoxin (primary outcome) and glycemia (secondary outcome). Tertiary outcomes include: gut and systemic inflammatory responses, microbiota composition and SCFAs, gut permeability, and circulating insulin and incretins.

EXPECTED RESULTS

MFGM is expected to decrease circulating endotoxin and glycemia without altering body mass. These improvements are anticipated to be accompanied by decreased gut permeability, decreased intestinal and circulating biomarkers of inflammation, increased circulating incretins, and beneficial antimicrobial and prebiotic effects in the gut microbiome.

CONCLUSIONS

Demonstration of improvements in gut barrier functions that limit endotoxemia and glycemia could help to establish direct evidence that full-fat dairy lowers cardiometabolic risk, especially in people with MetS.The clinical trial associated with this article has been registered at clinicaltrials.gov (NCT03860584).

Serum zonulin measured by enzyme-linked immunosorbent assay may not be a reliable marker of small intestinal permeability in healthy adults

The association between intestinal permeability (IP) and body composition remains unclear. The gold standard differential sugar-absorption test is arduous to complete, with zonulin being increasingly used as an independent biomarker of IP. This pilot study aimed to explore the association between small IP, zonulin concentrations, and body composition in healthy adults. The urinary lactulose-rhamnose ratio was used to measure small IP. Serum zonulin, lipopolysaccharide (LPS) and high-sensitivity C-reactive protein (hs-CRP) were analyzed in serum. Body composition was measured using dual-energy X-ray absorptiometry and anthropometric measurements were collected. In total, 34 participants were included (12 males, median age 28 years, body mass index 24 kg/m², waist circumference 77cm). No correlation was observed between the lactulose-rhamnose ratio and zonulin (r = -.016, P = .929). The lactulose-rhamnose ratio displayed a strong positive correlation with LPS (n 20, r = .536, P = .018) but did not correlate with body composition measures. Conversely, zonulin displayed a moderate positive correlation with waist circumference (r = .437, P = .042) in female participants and hs-CRP (r = .485, P = .004) in all participants. These findings raise important considerations for the measurement of small IP, warranting exploration in larger powered studies that address the limitations of the present study.

Intestinal-level anti-inflammatory bioactivities of catechin-rich green tea: Rationale, design, and methods of a double-blind, randomized, placebo-controlled crossover trial in metabolic syndrome and healthy adults

Metabolic endotoxemia initiates low-grade chronic inflammation in metabolic syndrome (MetS) and provokes the progression towards more advanced cardiometabolic disorders. Our recent works in obese rodent models demonstrate that catechin-rich green tea extract (GTE) improves gut barrier integrity to alleviate the translocation of gut-derived endotoxin and its consequent pro-inflammatory responses mediated through Toll-like receptor-4/nuclear factor κB (TLR4/NFκB) signaling. The objective of this clinical trial is to establish the efficacy of GTE to alleviate metabolic endotoxemia-associated inflammation in persons with MetS by improving gut barrier function. We plan a double-blind, placebo-controlled cross-over trial in persons with MetS and age- and gender-matched healthy persons (18-65 y; n = 20/group) who will receive a low-energy GTE-rich (1 g/day; 890 mg total catechins) confection snack food while following a low-polyphenol diet for 28 days. Assessments will include measures of circulating endotoxin (primary outcome) and secondary outcomes including biomarkers of endotoxin exposure, region-specific measures of intestinal permeability, gut microbiota composition, diversity, and functions, intestinal and systemic inflammatory responses, and catechins and microbiota-derived catechin metabolites. Study outcomes will provide the first report of the GTE-mediated benefits that alleviate gut barrier dysfunction in relation to endotoxemia-associated inflammation in MetS persons. This is expected to help establish an effective dietary strategy to mitigate the growing burden of MetS that currently affects ~35% of Americans.

The Gastrointestinal Exertional Heat Stroke Paradigm: Pathophysiology, Assessment, Severity, Aetiology and Nutritional Countermeasures

Exertional heat stroke (EHS) is a life-threatening medical condition involving thermoregulatory failure and is the most severe condition along a continuum of heat-related illnesses. Current EHS policy guidance principally advocates a thermoregulatory management approach, despite growing recognition that gastrointestinal (GI) microbial translocation contributes to disease pathophysiology. Contemporary research has focused to understand the relevance of GI barrier integrity and strategies to maintain it during periods of exertional-heat stress. GI barrier integrity can be assessed non-invasively using a variety of in vivo techniques, including active inert mixed-weight molecular probe recovery tests and passive biomarkers indicative of GI structural integrity loss or microbial translocation. Strenuous exercise is strongly characterised to disrupt GI barrier integrity, and aspects of this response correlate with the corresponding magnitude of thermal strain. The aetiology of GI barrier integrity loss following exertional-heat stress is poorly understood, though may directly relate to localised hyperthermia, splanchnic hypoperfusion-mediated ischemic injury, and neuroendocrine-immune alterations. Nutritional countermeasures to maintain GI barrier integrity following exertional-heat stress provide a promising approach to mitigate EHS. The focus of this review is to evaluate: (1) the GI paradigm of exertional heat stroke; (2) techniques to assess GI barrier integrity; (3) typical GI barrier integrity responses to exertional-heat stress; (4) the aetiology of GI barrier integrity loss following exertional-heat stress; and (5) nutritional countermeasures to maintain GI barrier integrity in response to exertional-heat stress.

Intestinal barrier function is maintained with aging - a comprehensive study in healthy subjects and irritable bowel syndrome patients

Animal studies have shown that intestinal barrier function is compromised with aging. We aimed to assess the effects of aging on intestinal barrier function in humans in vivo and ex vivo. In this cross-sectional study, healthy subjects and subjects with irritable bowel syndrome (IBS) of older (65–75 years) and young adult age (18–40 years) were compared. In vivo gastrointestinal site-specific permeability was assessed by a multi-sugar test, taking into account potential confounders. Sigmoid biopsies were collected from subgroups of healthy young adults and elderly for ex vivo Ussing chamber experiments, gene transcription of barrier-related genes and staining of junctional proteins. No significant differences between healthy young adults and elderly were found for small intestinal, colonic and whole gut permeability (P ≥ 0.142). In IBS patients, gastroduodenal and colonic permeability did not differ significantly (P ≥ 0.400), but small intestinal and whole gut permeability were higher in elderly versus young adults (P ≤ 0.009), mainly driven by the IBS-diarrhea subtype. Ussing chamber experiments with or without stressor (P ≥ 0.052), and relative expression of intestinal barrier-related genes (P ≥ 0.264) showed no significant differences between healthy elderly and young adults, as confirmed by immunofluorescent stainings. Overall, the functional capacity of the intestinal barrier is maintained in elderly.

Rapid HPLC method for monitoring of lactulose production with a high yield

An HPLC method suitable for rapid monitoring of lactulose production by isomerization from lactose was developed. The separation of lactose and lactulose under hydrophilic interaction liquid chromatography (HILIC) mode was achieved with resolution 1.5 within 5 min. Since isocratic elution was used, there is no extra time necessary for the column equilibration. Application of the method was illustrated on monitoring lactulose isomerization with catalysis of sodium hydroxide in the presence of sodium tetraborate at 70 °C (pH = 11). The conversion yield obtained for lactulose was 86%, and corresponding purity 76%. For the first time, a polyhydroxy stationary phase for separation of lactose and lactulose is reported.

The Impact of Pectin Supplementation on Intestinal Barrier Function in Healthy Young Adults and Healthy Elderly

Intestinal barrier function is suggested to decrease with aging and may be improved by pectin intake. The aim of this study was to investigate the effects of four weeks pectin supplementation on gastrointestinal barrier function in vivo and ex vivo in different age groups. In a randomized, double-blind, placebo-controlled, parallel study, 52 healthy young adults (18-40 years) and 48 healthy elderly (65-75 years) received 15 g/day pectin or placebo for four weeks. Pre- and post-intervention, in vivo gastrointestinal permeability by a multisugar test, and defense capacity in mucosal samples were assessed. Sigmoid biopsies were collected post-intervention from subgroups for Ussing chamber experiments and gene transcription of barrier-related genes. Pectin intervention did not affect in vivo gastroduodenal, small intestinal, colonic, and whole gut permeability in young adults nor in elderly (p ≥ 0.130). Salivary and fecal sIgA and serum IgA were not significantly different between pectin versus placebo in both age groups (p ≥ 0.128). In both young adults and elderly, no differences in transepithelial electrical resistance and fluorescein flux (p ≥ 0.164) and relative expression of genes analyzed (p ≥ 0.222) were found between pectin versus placebo. In conclusion, intestinal barrier function was not affected by four weeks pectin supplementation neither in healthy young adults nor in healthy elderly.

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.

Intestinal Permeability Measured by Urinary Sucrose Excretion Correlates with Serum Zonulin and Faecal Calprotectin Concentrations in UC Patients in Remission

Background and Aims

Ulcerative colitis (UC) is associated with an increased intestinal permeability, possibly through a dysbiosis of intestinal bacteria. We investigated which markers are most relevant to assess intestinal permeability in UC patients and whether probiotics had an effect on these markers.

Methods

In this twelve-week placebo-controlled randomized double-blind study, twenty-five subjects with UC in remission received either placebo or a multispecies probiotics. Samples of blood, urine, and faeces were taken at baseline, week 6, and week 12 to assess intestinal permeability and inflammation. Diaries and Bristol stool scale were kept to record stool frequency and consistency. Quality of life was scored from 32–224 with the inflammatory bowel disease questionnaire (IBD-Q).

Results

This group of UC patients, in clinical remission, did not show increased intestinal permeability at baseline of this study. During the study, no significant group or time effects were found for intestinal permeability measured by the 5-sugar absorption test, serum zonulin, and faecal zonulin. Likewise, the inflammatory markers C-reactive protein (CRP), calprotectin, and the cytokines IFNγ, TNFα, IL-6, and IL-10 were not significantly affected. Stool frequency and consistency were not significantly affected either. The IBD-Q score, 194 for the probiotics group and 195 for the placebo group, remained unaffected. Correlations were tested between all outcomes; urinary sucrose excretion was significantly correlated with serum zonulin (r = 0.62) and faecal calprotectin (r = 0.55). Faecal zonulin was not significantly correlated with any of the other markers.

Conclusion

Serum zonulin may be a more relevant biomarker of intestinal permeability than faecal zonulin, due to its correlation with other biomarkers of intestinal permeability. UC patients in remission did not show an effect of the probiotic treatment or a change in gut permeability. This should not discourage further studies because effects might be present during active disease or shortly after a flare up.

Increased Small Intestinal Permeability during Severe Acute Exacerbations of COPD

BACKGROUND

Disturbances of intestinal integrity, manifested by increased gastro-intestinal (GI) permeability, have been found in chronic obstructive pulmonary disease (COPD) patients during physical activity, often associated with intermittent hypoxic periods. Evidence about extrapulmonary organ disturbances, especially of the GI tract, during hospitalised acute exacerbation of COPD (AE-COPD) with hypoxaemic respiratory failure (RF) is lacking.

OBJECTIVE

The aim was to assess changes in GI permeability in patients with AE-COPD and during recovery 4 weeks later.

METHODS

All patients admitted to our hospital with AE-COPD accompanied by hypoxaemia at admission (PaO2 <8.7 kPa or O2 saturation <93%) were screened between October 2013 and February 2014. Patients with a history of GI or renal disease, chronic heart failure, or use of non-steroidal anti-inflammatory drugs in the 48 h before the test were excluded. GI permeability was assessed by evaluating urinary excretion ratios of the orally ingested sugars lactulose/L-rhamnose (L/R ratio), sucrose/L-rhamnose (Su/R ratio) and sucralose/erythritol (S/E ratio).

RESULTS

Seventeen patients with severe to very severe COPD completed the study. L/R ratio (×103) at admission of AE-COPD was significantly higher than in the recovery condition (40.9 [29.4-49.6] vs. 27.3 [19.5-47.7], p = 0.039), indicating increased small intestinal permeability. There were no significant differences in the individual sugar levels in urine nor in the 0- to 5-h urinary S/E and Su/R ratios between the 2 visits.

CONCLUSION

This is the first study showing increased GI permeability during hospitalised AE-COPD accompanied by hypoxaemic RF. Therefore, GI integrity in COPD patients is an attractive target for future research and for the development of interventions to alleviate the consequences of AE-COPD.

Human small intestine is capable of restoring barrier function after short ischemic periods

AIM

To assess intestinal barrier function during human intestinal ischemia and reperfusion (IR).

METHODS

In a human experimental model, 6 cm of jejunum was selectively exposed to 30 min of ischemia (I) followed by 30 and 120 min of reperfusion (R). A sham procedure was also performed. Blood and tissue was sampled at all-time points. Functional barrier function was assessed using dual-sugar absorption tests with lactulose (L) and rhamnose (R). Plasma concentrations of citrulline, an amino acid described as marker for enterocyte function were measured as marker of metabolic enterocytes restoration. Damage to the epithelial lining was assessed by immunohistochemistry for tight junctions (TJs), by plasma marker for enterocytes damage (I-FABP) and analyzed by electron microscopy (EM) using lanthanum nitrate as an electrondense marker.

RESULTS

Plasma L/R ratio’s were significantly increased after 30 min of ischemia (30I) followed by 30 min of reperfusion (30R) compared to control (0.75 ± 0.10 vs 0.20 ± 0.09, P < 0.05). At 120 min of reperfusion (120R), ratio’s normalized (0.17 ± 0.06) and were not significantly different from control. Plasma levels of I-FABP correlated with plasma L/R ratios measured at the same time points (correlation: 0.467, P < 0.01). TJs staining shows distortion of staining at 30I. An intact lining of TJs was again observed at 30I120R. Electron microscopy analysis revealed disrupted TJs after 30I with paracellular leakage of lanthanum nitrate, which restored after 30I120R. Furthermore, citrulline concentrations closely paralleled the histological perturbations during intestinal IR.

CONCLUSION

This study directly correlates histological data with intestinal permeability tests, revealing that the human gut has the ability of to withstand short episodes of ischemia, with morphological and functional recovery of the intestinal barrier within 120 min of reperfusion.

The effect of endurance exercise on intestinal integrity in well-trained healthy men

Exercise is one of the external factors associated with impairment of intestinal integrity, possibly leading to increased permeability and altered absorption. Here, we aimed to examine to what extent endurance exercise in the glycogen‐depleted state can affect intestinal permeability toward small molecules and protein‐derived peptides in relation to markers of intestinal function. Eleven well‐trained male volunteers (27 ± 4 years) ingested 40 g of casein protein and a lactulose/rhamnose (L/R) solution after an overnight fast in resting conditions (control) and after completing a dual – glycogen depletion and endurance – exercise protocol (first protocol execution). The entire procedure was repeated 1 week later (second protocol execution). Intestinal permeability was measured as L/R ratio in 5 h urine and 1 h plasma. Five‐hour urine excretion of betacasomorphin‐7 (BCM7), postprandial plasma amino acid levels, plasma fatty acid binding protein 2 (FABP‐2), serum pre‐haptoglobin 2 (preHP2), plasma glucagon‐like peptide 2 (GLP2), serum calprotectin, and dipeptidylpeptidase‐4 (DPP4) activity were studied as markers for excretion, intestinal functioning and recovery, inflammation, and BCM7 breakdown activity, respectively. BCM7 levels in urine were increased following the dual exercise protocol, in the first as well as the second protocol execution, whereas 1 h‐plasma L/R ratio was increased only following the first exercise protocol execution. FABP2, preHP2, and GLP2 were not changed after exercise, whereas calprotectin increased. Plasma citrulline levels following casein ingestion (iAUC) did not increase after exercise, as opposed to resting conditions. Endurance exercise in the glycogen depleted state resulted in a clear increase of BCM7 accumulation in urine, independent of DPP4 activity and intestinal permeability. Therefore, strenuous exercise could have an effect on the amount of food‐derived bioactive peptides crossing the epithelial barrier. The health consequence of increased passage needs more in depth studies.

Reinforcement of intestinal epithelial barrier by arabinoxylans in overweight and obese subjects: A randomized controlled trial: Arabinoxylans in gut barrier

BACKGROUND & AIMS

Obesity and metabolic diseases are associated with alterations in microbial composition and impaired gut barrier. Previous in vitro and animal studies have shown that arabinoxylans (AX) have the potential to modulate gut microbiota and gut barrier and therefore could have a protective role. Primary aim of the study was to investigate the effect of AX on intestinal permeability. Secondary aims included the effect of AX on gene transcription and protein expression of tight junctions (TJ), intestinal microbiota composition and activity, immune response and metabolic markers in overweight and obese individuals.

METHODS

In this randomized, double-blind, placebo-controlled trial, 47 overweight subjects were randomly assigned to groups receiving 7.5 g/d AX (n = 16), 15 g/d AX (n = 17) or 15 g/d placebo (n = 14) for 6 wks. Intestinal permeability was investigated using a multi-sugar test. Sigmoid colon tissue was obtained from a subgroup (n = 26) for analyzing gene transcription and mucosal expression of TJ proteins. Fecal samples were collected to assess microbial composition and activity. Furthermore, the production of cytokines by stimulated peripheral blood mononuclear cells (PBMCs) was examined. Blood was also sampled for measuring metabolic markers.

RESULTS

No significant changes in gastrointestinal permeability and TJ protein expression were observed after 6 wks AX supplementation compared to placebo. However, gene transcription of occludin was upregulated in the 7.5 g AX group, and transcription of claudin-3 and claudin-4 were upregulated in the 15 g AX group compared to placebo. Furthermore, fecal microbiota diversity was decreased after 6 wks 15 g AX treatment, but no change in relative abundance of dominant phyla was observed. AX intake significantly decreased fecal pH and increased fecal concentrations of total SCFAs, acetate, propionate and butyrate, compared to placebo. Additionally, a decreased TNFα production by stimulated PBMCs was observed after 15 g AX treatment. No changes in metabolic markers were detected.

CONCLUSIONS

Regular consumption of AX resulted in a more beneficial fermentation profile in overweight and obese individuals. Further studies are required to assess whether such fermentation profile will translate into improved gut barrier function and immune health. The trial has been registered at ClinicalTrials.gov with study ID number NCT01877044.

Endurance Exercise Increases Intestinal Uptake of the Peanut Allergen Ara h 6 after Peanut Consumption in Humans

Controlled studies on the effect of exercise on intestinal uptake of protein are scarce and underlying mechanisms largely unclear. We studied the uptake of the major allergen Ara h 6 following peanut consumption in an exercise model and compared this with changes in markers of intestinal permeability and integrity. Ten overnight-fasted healthy non-allergic men (n = 4) and women (n = 6) (23 ± 4 years) ingested 100 g of peanuts together with a lactulose/rhamnose (L/R) solution, followed by rest or by 60 min cycling at 70% of their maximal workload. Significantly higher, though variable, levels of Ara h 6 in serum were found during exercise compared to rest (Peak p = 0.03; area under the curve p = 0.006), with individual fold changes ranging from no increase to an increase of over 150-fold in the uptake of Ara h 6. Similarly, uptake of lactulose (2–18 fold change, p = 0.0009) and L/R ratios (0.4–7.9 fold change, p = 0.04) were significantly increased which indicates an increase in intestinal permeability. Intestinal permeability and uptake of Ara h 6 were strongly correlated (r = 0.77, p < 0.0001 for lactulose and Ara h 6). Endurance exercise after consumption may lead to increased paracellular intestinal uptake of food proteins.

The effects of Lactobacillus plantarum on small intestinal barrier function and mucosal gene transcription; a randomized double-blind placebo controlled trial

The aim of this study was to investigate the effects of three Lactobacillus plantarum strains on in-vivo small intestinal barrier function and gut mucosal gene transcription in human subjects. The strains were selected for their differential effects on TLR signalling and tight junction protein rearrangement, which may lead to beneficial effects in a stressed human gut mucosa. Ten healthy volunteers participated in four different intervention periods: 7-day oral intake of either L. plantarum WCFS1, CIP104448, TIFN101 or placebo, proceeded by a 4 weeks wash-out period. Lactulose-rhamnose ratio (an indicator of small intestinal permeability) increased after intake of indomethacin, which was given as an artificial stressor of the gut mucosal barrier (mean ratio 0.06 ± 0.04 to 0.10 ± 0.06, p = 0.001), but was not significantly affected by the bacterial interventions. However, analysis in small intestinal biopsies, obtained by gastroduodenoscopy, demonstrated that particularly L. plantarum TIFN101 modulated gene transcription pathways related to cell-cell adhesion with high turnover of genes involved in tight- and adhesion junction protein synthesis and degradation (e.g. actinin alpha-4, metalloproteinase-2). These effects were less pronounced for L. plantarum WCFS1 and CIP104448. In conclusion, L. plantarum TIFN101 induced the most pronounced probiotic properties with specific gene transcriptional effects on repair processes in the compromised intestine of healthy subjects.

Adaptation of exercise-induced stress in well-trained healthy young men

NEW FINDINGS

What is the central question of this study? Exercise is known to induce stress-related physiological responses, such as changes in intestinal barrier function. Our aim was to determine the test-retest repeatability of these responses in well-trained individuals. What is the main finding and its importance? Responses to strenuous exercise, as indicated by stress-related markers such as intestinal integrity markers and myokines, showed high test-retest variation. Even in well-trained young men an adapted response is seen after a single repetition after 1 week. This finding has implications for the design of studies aimed at evaluating physiological responses to exercise. Strenuous exercise induces different stress-related physiological changes, potentially including changes in intestinal barrier function. In the Protégé Study (ISRCTN14236739; www.isrctn.com), we determined the test-retest repeatability in responses to exercise in well-trained individuals. Eleven well-trained men (27 ± 4 years old) completed an exercise protocol that consisted of intensive cycling intervals, followed by an overnight fast and an additional 90 min cycling phase at 50% of maximal workload the next morning. The day before (rest), and immediately after the exercise protocol (exercise) a lactulose and rhamnose solution was ingested. Markers of energy metabolism, lactulose-to-rhamnose ratio, several cytokines and potential stress-related markers were measured at rest and during exercise. In addition, untargeted urine metabolite profiles were obtained. The complete procedure (Test) was repeated 1 week later (Retest) to assess repeatability. Metabolic effect parameters with regard to energy metabolism and urine metabolomics were similar for both the Test and Retest period, underlining comparable exercise load. Following exercise, intestinal permeability (1 h plasma lactulose-to-rhamnose ratio) and the serum interleukin-6, interleukin-10, fibroblast growth factor-21 and muscle creatine kinase concentrations were significantly increased compared with rest only during the first test and not when the test was repeated. Responses to strenuous exercise in well-trained young men, as indicated by intestinal markers and myokines, show adaptation in Test-Retest outcome. This might be attributable to a carry-over effect of the defense mechanisms triggered during the Test. This finding has implications for the design of studies aimed at evaluating physiological responses to exercise.

Effects of Supplementation of the Synbiotic Ecologic® 825/FOS P6 on Intestinal Barrier Function in Healthy Humans: A Randomized Controlled Trial

BACKGROUND AND AIMS

Probiotics, prebiotics and synbiotics have been suggested as dietary strategies to improve intestinal barrier function. This study aimed to assess the effect of two weeks synbiotic supplementation on intestinal permeability under basal and stressed conditions. Secondary aims were the assessment of two weeks synbiotic supplementation on systemic immune function and gastrointestinal symptoms including defecation pattern.

DESIGN

Twenty healthy adults completed a double-blind, controlled, randomized, parallel design study.

INTERVENTION

Groups either received synbiotic (1.5 × 1010 CFU Ecologic® 825 + 10 g fructo-oligosaccharides (FOS P6) per day) or control supplements for two weeks.

OUTCOMES

Intestinal segment specific permeability was assessed non-invasively by oral administration of multiple sugar probes and, subsequently, assessing the excretion of these probes in urine. This test was conducted at baseline and at the end of intervention, in the absence and in the presence of an indomethacin challenge. Indomethacin was applied to induce a compromised gut state. Plasma zonulin, cytokines and chemokines were measured at baseline and at the end of intervention. Gastrointestinal symptoms and stool frequency were recorded at baseline and daily during intervention.

RESULTS

Significantly more male subjects were in the synbiotic group compared to the control group (P = 0.025). Indomethacin significantly increased urinary lactulose/rhamnose ratio versus without indomethacin, both in the control group (P = 0.005) and in the synbiotic group (P = 0.017). Urinary sugar recoveries and ratios, plasma levels of zonulin, cytokines and chemokines, and gastrointestinal symptom scores were not significantly different after control or synbiotic intervention. Stool frequency within the synbiotic group was significantly increased during synbiotic intervention compared to baseline (P = 0.039) and higher compared to control intervention (P = 0.045).

CONCLUSION

Two weeks Ecologic® 825/FOS P6 supplementation increased stool frequency, but did not affect intestinal permeability neither under basal nor under indomethacin-induced stressed conditions, immune function or gastrointestinal symptoms in healthy adults.

(-)-Epigallocatechin-3-gallate decreases colonic inflammation and permeability in a mouse model of colitis, but reduces macronutrient digestion and exacerbates weight loss

SCOPE

(-)-Epigallocatechin-3-gallate (EGCG) has been reported to have putative health effects including the prevention of inflammation and obesity. Historically, polyphenols have been regarded as antinutritionals and while such effects may be beneficial in obese subjects, they may be deleterious in nutritionally compromised individuals.

METHODS AND RESULTS

We examined the effect of EGCG in the dextran sulfate sodium (DSS)-treated mouse model of ulcerative colitis. Following induction of colitis, mice were treated with EGCG (3.2 mg/g) as the sole source of drinking fluid for 3 days. EGCG treatment mitigated DSS-induced colon shortening and spleen enlargement. EGCG also decreased colonic protein levels of IL-1β, IL-6, and tumor necrosis factor-α, as well as colonic lipid peroxides compared to DSS-treated controls. We observed that EGCG reduced DSS-induced gastrointestinal permeability. These beneficial effects were offset by enhanced body weight loss in EGCG-treated mice compared to DSS-treated controls. These effects were related to decreased protein and lipid digestion in EGCG-treated mice compared to DSS-treated controls.

CONCLUSIONS

Our results suggest that although EGCG may exert anti-inflammatory effects, its ability to modulate macronutrient digestion may represent a dose-limiting adverse effect that must be considered in the context of its use for treating inflammatory bowel disease.

Development and validation of a sensitive UPLC-MS/MS method for the quantitation of [(13)C]sucrose in rat plasma, blood, and brain: Its application to the measurement of blood-brain barrier permeability

Accurate and reproducible measurement of blood-brain barrier (BBB) integrity is critical in the assessment of the pathophysiology of the central nervous system disorders and in monitoring therapeutic effects. The widely-used low molecular weight marker [(14)C]sucrose is non-specific in the absence of chromatographic separation. The purpose of this study was to develop and validate a sensitive and reproducible LC-MS/MS method for the analysis of stable isotope-modified [(13)C12]sucrose in brain, plasma, and blood to determine BBB permeability to sucrose. After addition of internal standard (IS, [(13)C6]sucrose), the marker and IS were recovered from diluted rat blood, plasma, and brain homogenate by protein precipitation using acetonitrile. The recovery of the marker and IS was almost quantitative (90-106%) for all three matrices. The recovered samples were directly injected into an isocratic UPLC system with a run time of 6 min. Mass spectrometry was conducted using multiple reaction monitoring in negative mode. The method was linear (r(2)≥0.99) in the concentration ranges tested for the diluted blood and plasma (10-1000 ng/mL) and brain homogenate (1-200 ng/mL). The lower limit of quantitation of the assay was 0.5 pg injected on column. The assay was validated (n=5) based on acceptable intra- and inter-run accuracy and precision values. The method was successfully used for the measurement of serial blood and plasma and terminal brain concentrations of [(13)C12]sucrose after a single intravenous dose (10 mg/kg) of the marker to rats. As expected, the apparent brain uptake clearance values of [(13)C12]sucrose were low in healthy rats. The method may be useful for determination of the BBB integrity in animal models.

L-citrulline improves splanchnic perfusion and reduces gut injury during exercise

PURPOSE

Splanchnic hypoperfusion is a physiological phenomenon during strenuous exercise. It has been associated with gastrointestinal symptoms and intestinal injury and may hamper athletic performance. We hypothesized that L-citrulline supplementation improves splanchnic perfusion and decreases intestinal injury by enhancing arginine availability. The aim of this study was to determine the effect of L-citrulline intake on splanchnic perfusion, intestinal injury, and barrier function during exercise.

METHODS

In this randomized, double-blind crossover study, 10 men cycled for 60 min at 70% of their maximum workload after L-citrulline (10 g) or placebo (L-alanine) intake. Splanchnic perfusion was assessed using gastric air tonometry. Sublingual microcirculation was evaluated by sidestream dark field imaging. Plasma amino acid levels and intestinal fatty acid binding protein concentrations, reflecting enterocyte damage, were assessed every 10 min. Urinary excretion of sugar probes was measured to evaluate intestinal permeability changes.

RESULTS

Oral L-citrulline supplementation enhanced plasma citrulline (1840.3 ± 142.3 µM) and arginine levels (238.5 ± 9.1 µM) compared with that in placebo (45.7 ± 4.8 µM and 101.5 ± 6.1 µM, respectively, P < 0.0001), resulting in increased arginine availability. Splanchnic hypoperfusion was prevented during exercise after L-citrulline ingestion (reflected by unaltered gapg-apCO2 levels), whereas gapg-apCO2 increased with placebo treatment (P < 0.01). Accordingly, L-citrulline intake resulted in an increased number of perfused small sublingual vessels compared with that in placebo (7.8 ± 6.0 vs -2.0 ± 2.4, P = 0.06). Furthermore, plasma intestinal fatty acid binding protein levels were attenuated during exercise after L-citrulline supplementation compared with that in placebo (AUC0-60 min, -185% ± 506% vs 1318% ± 553%, P < 0.01). No significant differences were observed for intestinal permeability.

CONCLUSIONS

Pre-exercise L-citrulline intake preserves splanchnic perfusion and attenuates intestinal injury during exercise in athletes compared with placebo, probably by enhancing arginine availability. These results suggest that oral L-citrulline supplementation is a promising intervention to combat splanchnic hypoperfusion-induced intestinal compromise.

Membrane-permeable tastants amplify β2-adrenergic receptor signaling and delay receptor desensitization via intracellular inhibition of GRK2's kinase activity

BACKGROUND

Amphipathic sweet and bitter tastants inhibit purified forms of the protein kinases GRK2, GRK5 and PKA activities. Here we tested whether membrane-permeable tastants may intracellularly interfere with GPCR desensitization at the whole cell context.

METHODS

β2AR-transfected cells and cells containing endogenous β2AR were preincubated with membrane-permeable or impermeable tastants and then stimulated with isoproterenol (ISO). cAMP formation, β2AR phosphorylation and β2AR internalization were monitored in response to ISO stimulation. IBMX and H89 inhibitors and GRK2 silencing were used to explore possible roles of PDE, PKA, and GRK2 in the tastants-mediated amplification of cAMP formation and the tastant delay of β2AR phosphorylation and internalization.

RESULTS

Membrane-permeable but not impermeable tastants amplified the ISO-stimulated cAMP formation in a concentration- and time-dependent manner. Without ISO stimulation, amphipathic tastants, except caffeine, had no effect on cAMP formation. The amplification of ISO-stimulated cAMP formation by the amphipathic tastants was not affected by PDE and PKA activities, but was completely abolished by GRK2 silencing. Amphipathic tastants delayed the ISO-induced GRK-mediated phosphorylation of β2ARs and GRK2 silencing abolished it. Further, tastants also delayed the ISO-stimulated β2AR internalization.

CONCLUSION

Amphipathic tastants significantly amplify β2AR signaling and delay its desensitization via their intracellular inhibition of GRK2.

GENERAL SIGNIFICANCE

Commonly used amphipathic tastants may potentially affect similar GPCR pathways whose desensitization depends on GRK2's kinase activity. Because GRK2 also modulates phosphorylation of non-receptor components in multiple cellular pathways, these gut-absorbable tastants may permeate into various cells, and potentially affect GRK2-dependent phosphorylation processes in these cells as well.

Rapid small intestinal permeability assay based on riboflavin and lactulose detected by bis-boronic acid appended benzyl viologens

Background

Although organoboronic acids are efficient high-throughput sugar sensors, they have not been pursued for gut permeability studies. A modification of the lactulose/mannitol assay is described by which small intestinal permeability is assessed at the time of urine collection using a lactulose/riboflavin ratio.

Methods

Volunteers ingested 50 mg riboflavin and either 5 g mannitol or 10 g lactulose. Urine was collected for 6 hrs. Riboflavin was assayed by autofluorescence. Riboflavin was removed by C18 solid phase extraction. Lactulose and mannitol were then assayed using 1,1′-bis(2-boronobenzyl)-4,4′-bipyridinium (4,4′oBBV) coupled to the fluorophore HPTS.

Results

The temporal profile over 6 hrs for riboflavin paralleled mannitol. Riboflavin recovery in urine was 11.1 ± 1.9 % (mean ± SEM, n = 7), similar to mannitol. There was selective binding of 4,4′oBBV to lactulose, likely involving cooperativity between the fructose and galactose moieties. Lower limits of detection and quantification were 90 and 364 μM. The lactulose assay was insensitive to other permeability probes (e.g., sucrose, sucralose) while tolerating glucose or lactose. This assay can be adapted to automated systems. Stability of 4,4′oBBV exceeds 4 years.

Conclusions

Riboflavin measured by autofluorescence combined with lactulose measured with 4,4′oBBV represents a useful new chemistry for rapid measurement of intestinal permeability with excellent stability, cost and throughput benefits.

Serotonergic reinforcement of intestinal barrier function is impaired in irritable bowel syndrome

BACKGROUND

Alterations in serotonergic (5-HT) metabolism and/or intestinal integrity have been associated with irritable bowel syndrome (IBS).

AIMS

To assess the effects of the precursor of 5-HT, 5-hydroxytryptophan (5-HTP), on mucosal 5-HT availability and intestinal integrity, and to assess potential differences between healthy controls and IBS patients.

METHODS

Fifteen IBS patients and 15 healthy volunteers participated in this randomised double-blind placebo-controlled study. Intestinal integrity was assessed by dual-sugar test and by determining the mucosal expression of tight junction proteins after ingestion of an oral bolus of 100 mg 5-HTP or placebo. Mucosal serotonergic metabolism was assessed in duodenal biopsy samples.

RESULTS

5-HTP administration significantly increased mucosal levels of 5-HIAA, the main metabolite of 5-HT, in both healthy controls (7.1 ± 1.7 vs. 2.5 ± 0.7 pmol/mg, 5-HTP vs. placebo, P = 0.02) and IBS patients (20.0 ± 4.8 vs. 8.1 ± 1.3 pmol/mg, 5-HTP vs. placebo, P = 0.02), with the latter group showing a significantly larger increase. Lactulose/L-rhamnose ratios were significantly lower after administration of 5-HTP (P < 0.05) in healthy controls and were accompanied by redistribution of zonula occludens-1 (ZO-1), pointing to reinforcement of the barrier. In IBS, expression of the tight junction proteins was significantly lower compared to healthy controls, and 5-HTP resulted in a further decrease in occludin expression.

CONCLUSIONS

Oral 5-HTP induced alterations in mucosal 5-HT metabolism. In healthy controls, a reinforcement of the intestinal barrier was seen whereas such reaction was absent in IBS patients. This could indicate the presence of a serotonin-mediated mechanism aimed to reinforce intestinal barrier function, which seems to dysfunction in IBS patients.

Small intestinal permeability is increased in diarrhoea predominant IBS, while alterations in gastroduodenal permeability in all IBS subtypes are largely attributable to confounders

BACKGROUND

Intestinal permeability has been studied in small groups of IBS patients with contrasting findings.

AIMS

To assess intestinal permeability at different sites of the GI tract in different subtypes of well-characterised IBS patients and healthy controls (HC), and to assess potential confounding factors.

METHODS

IBS patients and HC underwent a multi-sugar test to assess site-specific intestinal permeability. Sucrose excretion and lactulose/rhamnose ratio in 0-5 h urine indicated gastroduodenal and small intestinal permeability, respectively. Sucralose/erythritol ratio in 0-24 h and 5-24 h urine indicated whole gut and colonic permeability, respectively. Linear regression analysis was used to assess the association between IBS groups and intestinal permeability and to adjust for age, sex, BMI, anxiety or depression, smoking, alcohol intake and use of medication.

RESULTS

Ninety-one IBS patients, i.e. 37% IBS-D, 23% IBS-C, 33% IBS-M and 7% IBS-U and 94 HC were enrolled. Urinary sucrose excretion was significantly increased in the total IBS group [μmol, median (Q1;Q3): 5.26 (1.82;11.03) vs. 2.44 (0.91;5.85), P < 0.05], as well as in IBS-C and IBS-D vs. HC. However, differences attenuated when adjusting for confounders. The lactulose/rhamnose ratio was increased in IBS-D vs. HC [0.023 (0.013;0.038) vs. 0.014 (0.008;0.025), P < 0.05], which remained significant after adjustment for confounders. No difference was found in 0-24 and 5-24 h sucralose/erythritol ratio between groups.

CONCLUSIONS

Small intestinal permeability is increased in patients with IBS-D compared to healthy controls, irrespective of confounding factors. Adjustment for confounders is necessary when studying intestinal permeability, especially in a heterogeneous disorder such as IBS.

Disturbed intestinal integrity in patients with COPD: effects of activities of daily living

BACKGROUND

COPD is accepted to be a multicomponent disease with various comorbidities. To our knowledge, the contribution of the GI tract to the systemic manifestation of COPD has never been investigated. This metabolically active organ may experience recurring local oxygen deficits during daily life, leading to disturbed intestinal integrity in patients with COPD.

METHODS

Eighteen patients with moderate COPD (mean FEV₁, 55 ± 3% predicted) and 14 matched healthy control subjects were tested on two occasions: a baseline measurement at rest and, on another day, during the performance of activities of daily living (ADLs). To assess enterocyte damage, plasma intestinal fatty acid binding protein (IFABP) levels were determined, whereas urinary excretion of orally ingested sugar probes was measured using liquid chromatography and mass spectrometry to assess GI permeability.

RESULTS

Plasma IFABP concentrations were not different between patients with COPD and healthy control subjects at rest. In contrast, 0- to 3-h urinary lactulose to rhamnose and sucralose to erythritol ratios and 5- to 24-h urinary sucralose to erythritol ratios were significantly higher in patients with COPD compared with control subjects, indicating increased permeability of the small intestine and colon. Furthermore, the performance of ADLs led to significantly increased plasma IFABP concentrations in patients with COPD but not in control subjects. Similarly, the intestinal permeability difference between patients and control subjects was intensified.

CONCLUSIONS

Besides an altered intestinal permeability in patients with COPD when at rest, performing ADLs led to enterocyte damage in addition to intestinal hyperpermeability in patients with COPD but not in control subjects, indicating functional alteration in the GI tract. Hence, intestinal compromise should be considered as a new component of the multisystem disorder COPD.

TRIAL REGISTRY

ISRCTN Register; No.: ISRCTN33686980; URL: www.controlled-trials.com.

Large intestine permeability is increased in patients with compensated liver cirrhosis

Intestinal barrier dysfunction, facilitating translocation of bacteria and bacterial products, plays an important role in the pathophysiology of liver cirrhosis and its complications. Increased intestinal permeability has been found in patients with liver cirrhosis, but data on small and large intestine permeability and tight junctions (TJs) in patients with compensated cirrhosis are scarce. We aimed to investigate both small and large intestine permeability in patients with stable compensated cirrhosis compared with healthy controls and evaluated the expression of TJ proteins in mucosal biopsies at duodenal and sigmoid level. Intestinal permeability was assessed in 26 patients with compensated cirrhosis and 27 matched controls using a multisugar test. Duodenal and sigmoid biopsies were available from a subgroup for analyses of gene transcription and expression of key TJ proteins by qRT-PCR and ELISA, respectively. Median 0-5-h urinary sucrose excretion and lactulose/rhamnose ratio were comparable between patients with compensated cirrhosis and controls, whereas 5-24-h urinary sucralose/erythritol ratio was increased in these patients. Downregulation of gene transcription was found for claudin-3 in duodenal biopsies and claudin-4 in sigmoid biopsies, and at the protein level occludin expression was significantly increased in both duodenal and sigmoid biopsies. This study shows that gastroduodenal and small intestine permeability are not altered, whereas large intestine permeability is increased in patients with stable compensated cirrhosis. Only limited alterations were found regarding the expression of TJ proteins in both the small and large intestine.

Chenodeoxycholic acid reduces intestinal permeability in newly weaned piglets

Piglets are highly susceptible to gut health-related problems. Intravenously administered chenodeoxycholic acid (CDCA) affects gut health mediated through glucagon-like peptide 2 (GLP-2). To test whether CDCA is a suitable feed additive for improving gut health, a trial was performed with newly weaned (21 d) piglets offered a diet with or without 60 mg CDCA/kg feed (n = 24/treatment). Upon weaning, piglets were fasted for 16 h and then intragastrically dosed with 20 g test feed in 40 g water. Subsequently, a jugular blood sample was taken on 45, 90, 135, or 180 min for analysis of GLP-2, peptide YY (PYY), and glucose. Afterwards, piglets were offered the experimental diets ad libitum. On days 3.5, 7.5, and 10.5 after weaning, serum responses to an intragastric dose of lactulose and Co-EDTA were tested at 2 h after dosing in 8 piglets per treatment. Immediately thereafter, piglets were euthanized, intestines were harvested, and permeability was measured ex vivo using the everted gut sac technique with 4 kDa fluorescein isothiocyanato (FITC)-dextran as marker at 25, 50, and 75% of the length of the small intestine. Dietary CDCA did not affect (P > 0.05) ADFI, ADG, G:F, blood glucose, and plasma GLP-2 and PYY. Serum cobalt and lactulose at day 10.5 tended to be lower in CDCA pigs compared with control pigs. Serum cobalt and lactulose concentrations were positively correlated (r = 0.67; P < 0.01). In conclusion, CDCA tended to reduce intestinal permeability at 10.5 d after weaning when fed to newly weaned piglets, implying that CDCA deserves further study as a means for improving intestinal health. The positive correlation found between Co-EDTA and lactulose indicates that both marker molecules measure similar change in permeability.

Aggravation of exercise-induced intestinal injury by Ibuprofen in athletes

INTRODUCTION

Nonsteroidal anti-inflammatory drugs are commonly used by athletes to prevent anticipated exercise-induced pain, thereby putatively improving physical performance. However, these drugs may have potentially hazardous effects on the gastrointestinal (GI) mucosa during strenuous physical exercise. The aim of the current study was to determine the effect of oral ibuprofen administration before exercise on GI integrity and barrier function in healthy individuals.

METHODS

Nine healthy, trained men were studied on four different occasions: 1) 400 mg ibuprofen twice before cycling, 2) cycling without ibuprofen, 3) 400 mg ibuprofen twice at rest, and 4) rest without ibuprofen intake. To assess small intestinal injury, plasma intestinal fatty acid binding protein (I-FABP) levels were determined, whereas urinary excretion of orally ingested multisugar test probes was measured using liquid chromatography and mass spectrometry to assess GI permeability.

RESULTS

Both ibuprofen consumption and cycling resulted in increased I-FABP levels, reflecting small intestinal injury. Levels were higher after cycling with ibuprofen than after cycling without ibuprofen, rest with ibuprofen, or rest without ibuprofen (peak I-FABP, 875 ± 137, 474 ± 74, 507 ± 103, and 352 ± 44 pg·mL, respectively, P < 0.002). In line, small intestinal permeability increased, especially after cycling with ibuprofen (0-2 h urinary lactulose/rhamnose ratio, 0.08 (0.04-0.56) compared with 0.04 (0.00-0.20), 0.05 (0.01-0.07), and 0.01 (0.01-0.03), respectively), reflecting loss of gut barrier integrity. Interestingly, the extent of intestinal injury and barrier dysfunction correlated significantly (RS = 0.56, P < 0.001).

CONCLUSION

This is the first study to reveal that ibuprofen aggravates exercise-induced small intestinal injury and induces gut barrier dysfunction in healthy individuals. We conclude that nonsteroidal anti-inflammatory drugs consumption by athletes is not harmless and should be discouraged.