Lactulose/mannitol test and specificity, sensitivity, and area under curve of intestinal permeability parameters in patients with liver cirrhosis and Crohn's disease

A Rapid and Reliable Spectrofluorimetric Method to Measure the Urinary Lactulose/Mannitol Ratio for Dysbiosis Assessment

Gut microbiota plays a crucial role in human health homeostasis, and the result of its alteration, known as dysbiosis, leads to several pathologies (e.g., inflammatory bowel disease, metabolic syndrome, and Crohn's disease). Traditional methods used to assess dysbiosis include the dual sugar absorption test and the urinary lactulose/mannitol ratio (LMR) measurement using mass spectrometry. Despite its precision, this approach is costly and requires specialized equipment. Hence, we developed a rapid and reliable spectrofluorimetric method for measuring LMR in urine, offering a more accessible alternative. This spectrofluorimetric assay quantifies the fluorescence of nicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotide phosphate (NADPH) produced during the enzymatic oxidation of mannitol and lactulose, respectively. The assay requires 100 µL of urine samples and detects LMR values lower (eubiosis) and higher (dysbiosis) than 0.05, ultimately being amenable to high-throughput screening and automatization, making it practical for clinical and research settings. A validation of the method demonstrated its high precision, accuracy, and robustness. Additionally, this study confirmed analyte stability under various storage conditions, ensuring reliable results even with delayed analysis. Overall, this spectrofluorimetric technique reduces costs, time, and the environmental impact associated with traditional mass spectrometry methods, making it a viable option for widespread use in the assessment of dysbiosis.

Can Diet Alter the Intestinal Barrier Permeability in Healthy People? A Systematic Review

Dietary factors can modify the function of the intestinal barrier, causing permeability changes. This systematic review analyzed evidence on the link between diet or dietary interventions and changes in intestinal barrier permeability (IBP) in healthy individuals. A systematic search for primary studies was conducted using the virtual databases EMBASE, PubMed, Web of Science, CINAHL, and Scopus. This review adhered to PRISMA 2020 guidelines, assessing the methodological quality using the Newcastle-Ottawa scale for observational studies and ROB 2.0 for randomized clinical trials. Out of 3725 studies recovered, 12 were eligible for review. Chicory inulin and probiotics reduced IBP in adults with a moderate GRADE level of evidence. The opposite result was obtained with fructose, which increased IBP in adults, with a very low GRADE level of evidence. Only intervention studies with different dietary components were found, and few studies evaluated the effect of specific diets on the IBP. Thus, there was no strong evidence that diet or dietary interventions increase or decrease IBP in healthy individuals. Studies on this topic are necessary, with a low risk of bias and good quality of evidence generated, as there is still little knowledge on healthy populations.

Role of Stress on Driving the Intestinal Paracellular Permeability

The gut epithelium is a polarized monolayer that exhibits apical and basolateral membrane surfaces. Monolayer cell components are joined side by side via protein complexes known as tight junction proteins (TJPs), expressed at the most apical extreme of the basolateral membrane. The gut epithelium is a physical barrier that determinates intestinal permeability, referred to as the measurement of the transit of molecules from the intestinal lumen to the bloodstream or, conversely, from the blood to the gut lumen. TJPs play a role in the control of intestinal permeability that can be disrupted by stress through signal pathways triggered by the ligation of receptors with stress hormones like glucocorticoids. Preclinical studies conducted under in vitro and/or in vivo conditions have addressed underlying mechanisms that account for the impact of stress on gut permeability. These mechanisms may provide insights for novel therapeutic interventions in diseases in which stress is a risk factor, like irritable bowel syndrome. The focus of this study was to review, in an integrative context, the neuroendocrine effects of stress, with special emphasis on TJPs along with intestinal permeability.

Design and rationale for the SIB trial: a randomized parallel comparison of semaglutide versus placebo on intestinal barrier function in type 2 diabetes mellitus

Objective

To describe the rationale and design of the SIB trial, an interventional clinical trial testing the hypothesis that subcutaneous (s.c.) once-weekly semaglutide can improve intestinal permeability and reduce systemic inflammation in participants with type 2 diabetes (T2D) and obesity.

Methods

SIB (NCT04979130) is an investigator-initiated, single-center randomized, double-blinded, placebo-controlled clinical study being conducted at the University of Colorado Anschutz Medical Campus. The primary objective of this novel trial is to test the hypothesis that subcutaneous (s.c.) once-weekly semaglutide could improve intestinal permeability and reduce systemic inflammation in participants with T2D and obesity. Eligible participants had a diagnosis of type 2 diabetes, elevated body mass index, and evidence of systemic inflammation. Participants were randomized 1:1 to s.c. semaglutide or placebo. Participants were assessed for intestinal permeability and markers of inflammation at baseline, mid-study, and at the end of the study. Efficacy assessments were based on the analysis of the following: lactulose:mannitol ratio test, serum lipopolysaccharide-binding protein (LBP), fecal calprotectin, inflammatory biomarkers (IL-6, TNF, IL-1, IL-8, hs-CRP), and HbA1c. All participants who enrolled in the trial provided written informed consent after having received written and oral information on the trial. The risks of semaglutide use were minimized by administration according to FDA-labeled use and close monitoring for adverse events.

Discussion

SIB is the first study to examine the effects of GLP-1 receptor agonists on intestinal permeability in humans and will provide important data on their impact on systemic inflammation and intestinal permeability in the setting of T2D and obesity.

Inflammation, Autoinflammation and Autoimmunity in Inflammatory Bowel Diseases

In this review, the role of innate and adaptive immunity in the pathogenesis of inflammatory bowel diseases (IBD) is reported. In IBD, an altered innate immunity is often found, with increased Th17 and decreased Treg cells infiltrating the intestinal mucosa. An associated increase in inflammatory cytokines, such as IL-1 and TNF-α, and a decrease in anti-inflammatory cytokines, such as IL-10, concur in favoring the persistent inflammation of the gut mucosa. Autoinflammation is highlighted with insights in the role of inflammasomes, which activation by exogenous or endogenous triggers might be favored by mutations of NOD and NLRP proteins. Autoimmunity mechanisms also take place in IBD pathogenesis and in this context of a persistent immune stimulation by bacterial antigens and antigens derived from intestinal cells degradation, the adaptive immune response takes place and results in antibodies and autoantibodies production, a frequent finding in these diseases. Inflammation, autoinflammation and autoimmunity concur in altering the mucus layer and enhancing intestinal permeability, which sustains the vicious cycle of further mucosal inflammation.

Intestinal Barrier Permeability in Obese Individuals with or without Metabolic Syndrome: A Systematic Review

Altered intestinal barrier permeability has been associated with obesity and its metabolic and inflammatory complications in animal models. The purpose of this systematic review is to assess the evidence regarding the association between obesity with or without Metabolic Syndrome (MetS) and alteration of the intestinal barrier permeability in humans. A systematic search of the studies published up until April 2022 in Latin America & Caribbean Health Sciences Literature (LILACS), PubMed, Scopus, Embase, and ScienceDirect databases was conducted. The methodological quality of the studies was assessed using the Newcastle–Ottawa scale (NOS) and the Agency for Healthcare Research and Quality (AHRQ) checklist. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework was used to assess the quality of the evidence. Eight studies were included and classified as moderate to high quality. Alteration of intestinal barrier permeability was evaluated by zonulin, lactulose/mannitol, sucralose, sucrose, lactulose/L-rhamnose, and sucralose/erythritol. Impaired intestinal barrier permeability measured by serum and plasma zonulin concentration was positively associated with obesity with MetS. Nonetheless, the GRADE assessment indicated a very low to low level of evidence for the outcomes. Thus, clear evidence about the relationship between alteration of human intestinal barrier permeability, obesity, and MetS was not found.

Individuals with Metabolic Syndrome Show Altered Fecal Lipidomic Profiles with No Signs of Intestinal Inflammation or Increased Intestinal Permeability

BACKGROUND

Metabolic Syndrome (MetS) is a clinical diagnosis where patients exhibit three out of the five risk factors: hypertriglyceridemia, low high-density lipoprotein (HDL) cholesterol, hyperglycemia, elevated blood pressure, or increased abdominal obesity. MetS arises due to dysregulated metabolic pathways that culminate with insulin resistance and put individuals at risk to develop various comorbidities with far-reaching medical consequences such as non-alcoholic fatty liver disease (NAFLD) and cardiovascular disease. As it stands, the exact pathogenesis of MetS as well as the involvement of the gastrointestinal tract in MetS is not fully understood. Our study aimed to evaluate intestinal health in human subjects with MetS.

METHODS

We examined MetS risk factors in individuals through body measurements and clinical and biochemical blood analysis. To evaluate intestinal health, gut inflammation was measured by fecal calprotectin, intestinal permeability through the lactulose-mannitol test, and utilized fecal metabolomics to examine alterations in the host-microbiota gut metabolism.

RESULTS

No signs of intestinal inflammation or increased intestinal permeability were observed in the MetS group compared to our control group. However, we found a significant increase in 417 lipid features of the gut lipidome in our MetS cohort. An identified fecal lipid, diacyl-glycerophosphocholine, showed a strong correlation with several MetS risk factors. Although our MetS cohort showed no signs of intestinal inflammation, they presented with increased levels of serum TNFα that also correlated with increasing triglyceride and fecal diacyl-glycerophosphocholine levels and decreasing HDL cholesterol levels.

CONCLUSION

Taken together, our main results show that MetS subjects showed major alterations in fecal lipid profiles suggesting alterations in the intestinal host-microbiota metabolism that may arise before concrete signs of gut inflammation or intestinal permeability become apparent. Lastly, we posit that fecal metabolomics could serve as a non-invasive, accurate screening method for both MetS and NAFLD.

A Simple, Robust, and Convenient HPLC Assay for Urinary Lactulose and Mannitol in the Dual Sugar Absorption Test

Background: Heterogeneous laborious analytical methodologies for the determination of urinary lactulose and mannitol limit their utility in intestinal permeability testing. Methods: We developed an assay using a Shimadzu HPLC system, an Aminex HPX87C column, and refractive index detection. The test was calibrated using a series of dilutions from standard stock solutions of lactulose and mannitol ‘spiked’ into urine samples. The utility to quantify urinary excretion during the dual sugar absorption test over 6 h was also determined. Results: Lactulose and mannitol were eluted isocratically at 5.7 and 10.1 min, respectively, with water as a mobile phase at a flow rate of 0.3 mL min⁻¹, 858 psi, 60 °C. The calibration curves for both sugars were linear up to 500 µg mL⁻¹ with a limit of detection in standard solutions at 4 µg mL⁻¹ and in ‘spiked’ urine samples at 15 µg mL⁻¹. The intra-assay and inter-assay CVs were between 2.0–5.1% and 2.0–5.1% for lactulose and 2.5–4.4% and 2.8–3.9% for mannitol. The urinary profiles of the 6 h absorption of lactulose and mannitol showed similar peak-retention times to standard solutions and were well-resolved at 5.9 and 10.4 min, respectively. Conclusions: The assay was easy to automate, using commonly available equipment and convenient requiring no prior laborious sample derivatization. The simplicity, reproducibility, and robustness of this assay facilitates its use in routine clinical settings for the quantification of intestinal permeability.

A case for improved assessment of gut permeability: a meta-analysis quantifying the lactulose:mannitol ratio in coeliac and Crohn's disease

BACKGROUND

A widely used method in assessing small bowel permeability is the lactulose:mannitol test, where the lactulose:mannitol ratio (LMR) is measured. However, there is discrepancy in how the test is conducted and in the values of LMR obtained across studies. This meta-analysis aims to determine LMR in healthy subjects, coeliac and Crohn's disease.

METHODS

A literature search was performed using PRISMA guidance to identify studies assessing LMR in coeliac or Crohn's disease. 19 studies included in the meta-analysis measured gut permeability in coeliac disease, 17 studies in Crohn's disease. Outcomes of interest were LMR values and comparisons of standard mean difference (SMD) and weighted mean difference (WMD) in healthy controls, inactive Crohn's, active Crohn's, treated coeliac and untreated coeliac. Pooled estimates of differences in LMR were calculated using the random effects model.

RESULTS

Pooled LMR in healthy controls was 0.014 (95% CI: 0.006-0.022) while pooled LMRs in untreated and treated coeliac were 0.133 (95% CI: 0.089-0.178) and 0.037 (95% CI: 0.019-0.055). In active and inactive Crohn's disease, pooled LMRs were 0.093 (95% CI: 0.031-0.156) and 0.028 (95% CI: 0.015-0.041). Significant differences were observed in LMR between: (1) healthy controls and treated coeliacs (SMD = 0.409 95% CI 0.034 to 0.783, p = 0.032), (2) healthy controls and untreated coeliacs (SMD = 1.362 95% CI: 0.740 to 1.984, p < 0.001), (3) treated coeliacs and untreated coeliacs (SMD = 0.722 95% CI: 0.286 to 1.157, p = 0.001), (4) healthy controls and inactive Crohn's (SMD = 1.265 95% CI: 0.845 to 1.686, p < 0.001), (5) healthy controls and active Crohn's (SMD = 2.868 95% CI: 2.112 to 3.623, p < 0.001), and (6) active Crohn's and inactive Crohn's (SMD = 1.429 (95% CI: 0.580 to 2.278, p = 0.001). High heterogeneity was observed, which was attributed to variability in protocols used across different studies.

CONCLUSION

The use of gut permeability measurements in screening and monitoring of coeliac and Crohn's disease is promising. LMR is useful in performing this function with significant limitations. More robust alternative tests with higher degrees of clinical evidence are needed if measurements of gut permeability are to find widespread clinical use.

IL-1β and the Intestinal Epithelial Tight Junction Barrier

The intestinal epithelial tight junction (TJ) barrier controls the paracellular permeation of contents from the intestinal lumen into the intestinal tissue and systemic circulation. A defective intestinal TJ barrier has been implicated as an important pathogenic factor in inflammatory diseases of the gut including Crohn's disease, ulcerative colitis, necrotizing enterocolitis, and celiac disease. Previous studies have shown that pro-inflammatory cytokines, which are produced during intestinal inflammation, including interleukin-1β (IL-1β), tumor necrosis factor-α, and interferon-γ, have important intestinal TJ barrier-modulating actions. Recent studies have shown that the IL-1β-induced increase in intestinal TJ permeability is an important contributing factor of intestinal inflammation. The IL-1β-induced increase in intestinal TJ permeability is mediated by regulatory signaling pathways and activation of nuclear transcription factor nuclear factor-κB, myosin light chain kinase gene activation, and post-transcriptional occludin gene modulation by microRNA and contributes to the intestinal inflammatory process. In this review, the regulatory role of IL-1β on intestinal TJ barrier, the intracellular mechanisms that mediate the IL-1β modulation of intestinal TJ permeability, and the potential therapeutic targeting of the TJ barrier are discussed.

Assessment of small-intestine permeability in healthy Nigerian children is altered by urinary volume and voiding status

Objective

This study aimed to uncover the effect of voided urinary volume on small intestine permeability ratios in healthy children.

Methods

We assessed small intestine permeability in 155 apparently healthy children, aged 3–5 years old, without any visible symptoms of disease, in a rural, malaria-endemic setting in Nigeria, using a multi-sugar test solution, comprising lactulose, sucrose, mannitol, and rhamnose. Children were categorized into low urinary volume (LV) and high urinary volume (HV), based on the volume of urine voided per kg body weight per hour. LV children voided less than 25^th percentile of the total population, while HV children voided greater than 75^th percentile of the total population. Urinary volume excreted over a 90-minute period after administration of the test solution was measured, and differences in sugar ratios were compared between children with high (HV) and low urinary volumes (LV), as well as between children who voided (VC) or who were not able to void (NVC) before administration of the test solution.

Results

Urinary mannitol and rhamnose recovery were 44% (p = 0.002) and 77% (p<0.001) higher in HV children compared to LV children respectively, while urinary lactulose recovery was 34% lower (p = 0.071). There was no difference in urinary sucrose recovery between groups (p = 0.74). Lactulose-mannitol ratio, lactulose-rhamnose ratio and sucrose-rhamnose ratio were all significantly higher in children in the LV group compared to children in the HV group (p<0.001). In a multiple regression analysis, urinary volume and voiding status combined, explained 13%, 23% and 7% of the variation observed in lactulose-mannitol, lactulose-rhamnose and sucrose-rhamnose ratios, respectively.

Conclusion

Sugar permeability ratios vary significantly with total urinary volume in multi-sugar small-intestine permeability tests. Voiding status before sugar administration appears to influence lactulose recovery, lactulose-rhamnose and sucrose-rhamnose ratios independently of total urinary volume. Evidence from this study suggests the need to take urinary volume into account when conducting multi-sugar small-intestine permeability tests.

Prebiotic Inulin Supplementation and Peripheral Insulin Sensitivity in adults at Elevated Risk for Type 2 Diabetes: A Pilot Randomized Controlled Trial

Prediabetes affects 84.1 million adults, and many will progress to type 2 diabetes (T2D). The objective of this proof-of-concept trial was to determine the efficacy of inulin supplementation to improve glucose metabolism and reduce T2D risk. Adults (n = 24; BMI: 31.3 ± 2.9 kg/m²; age: 54.4 ± 8.3 years) at risk for T2D were enrolled in this controlled feeding trial and consumed either inulin (10 g/day) or placebo (maltodextrin, 10 g/day) for six weeks. Assessments included peripheral insulin sensitivity, fasting glucose, and insulin, HOMA-IR, in vivo skeletal muscle substrate preference, Bifidobacteria copy number, intestinal permeability, and endotoxin concentrations. Participant retention was 92%. There were no baseline group differences except for fasting insulin (p = 0.003). The magnitude of reduction in fasting insulin concentrations with inulin (p = 0.003, inulin = Δ-2.9, placebo = Δ2.3) was attenuated after adjustment for baseline concentrations (p = 0.04). After adjusting for baseline values, reduction in HOMA-IR with inulin (inulin = Δ-0.40, placebo=Δ0.27; p = 0.004) remained significant. Bifidobacteria 16s increased (p = 0.04; inulin = Δ3.1e⁹, placebo = Δ-8.9e⁸) with inulin supplementation. Despite increases in gut Bifidobacteria, inulin supplementation did not improve peripheral insulin sensitivity. These findings question the need for larger investigations of inulin and insulin sensitivity in this population.

Leaky Gut and Gut-Liver Axis in Liver Cirrhosis: Clinical Studies Update

Portal blood flows into the liver containing the gut microbiome and its products such as endotoxin and bacterial DNA. The cirrhotic liver acts and detoxifies as the initial site of microbial products. In so-called "leaky gut," the increased intestinal permeability for bacteria and their products constitutes an important pathogenetic factor for major complications in patients with liver cirrhosis. Prolonged gastric and small intestinal transit may induce intestinal bacterial overgrowth, a condition in which colonic bacteria translocate into the small gut. Cirrhotic patients further show gut dysbiosis characterized by an overgrowth of potentially pathogenic bacteria and a decrease in autochthonous nonpathogenic bacteria. Pathological bacterial translocation (BT) is a contributing factor in the development of various severe complications. Bile acids (BAs) undergo extensive enterohepatic circulation and play important roles in the gut-liver axis. BT-induced inflammation prevents synthesis of BAs in the liver through inhibition of BA-synthesizing enzyme CYP7A1. A lower abundance of 7α-dehydroxylating gut bacteria leads to decreased conversion of primary to secondary BAs. Decreases in total and secondary BAs may play an important role in the gut dysbiosis characterized by a proinflammatory and toxic gut microbiome inducing BT and endotoxemia, as addressed in my previous reviews. Selective intestinal decontamination by the use of various antimicrobial drugs for management of complications has a long history. Lactobacillus GG decreasing endotoxemia is reported to improve the microbiome with beneficial changes in amino acid, vitamin and secondary BA metabolism. Current approaches for hepatic encephalopathy are the use of nonabsorbable antibiotics and disaccharides. Probiotics may become an additional therapeutic option for advanced liver cirrhosis.

Adipose Tissue T Regulatory Cells: Implications for Health and Disease

Obesity dramatically increases the risk of numerous conditions, including type 2 diabetes mellitus and other components of the metabolic syndrome. Pro-inflammatory changes that occur in adipose tissue are critical to the pathogenesis of these obesity-induced complications. Adipose tissue is one of the body's largest endocrine organs, and the cells that comprise the adipose tissue immunoenvironment secrete multiple factors (including adipokines and cytokines) that impact systemic metabolism. In particular, immunosuppressive regulatory T cells (Tregs) decline in obesity, partly in response to its complex interaction with adipocytes, and this decline contributes to disruption of the typical homeostasis observed in lean adipose tissue. Although the regulation of Treg differentiation, function, and enrichment is incompletely understood, factors including various cell-surface co-stimulatory molecules, certain lipid species, and cytokines such as PPARγ, adiponectin, and leptin are important mediators. It is also clear that there may be depot-specific differences in Tregs, rendering adipose tissue Tregs distinct from lymphoid or circulating Tregs, with implications on maintenance and functionality. While most of these findings are derived from studies in murine models, comparatively little is known about the human adipose tissue Treg signature, which requires further investigation.

DeepA-RBPBS: A hybrid convolution and recurrent neural network combined with attention mechanism for predicting RBP binding site

It's important to infer the binding site of RNA-binding proteins (RBP) for understanding the interaction between RBP and its RNA targets and decipher the mechanisms of transcriptional regulation. However, experimental detection of RBP binding sites is still time-intensive and expensive. Algorithms based on machine learning can speed up detection of RBP binding sites. In this article, we propose a new deep learning method, DeepA-RBPBS, which can use RNA sequences and structural features to predict RBP binding site. DeepA-RBPBS uses CNN and BiGRU to extract sequences and structural features without long-term dependence issues. It also utilizes an attention mechanism to enhance the contribution of key features. The comparison shows that the performance of DeepA-RBPBS is better than that of the state-of-the-art predictors. In the testing on 31 datasets of CLIP-seq experiments over 19 proteins, MCC (AUC) is 8% (5%) higher than those of the latest method based on deep learning, iDeepS. We also apply DeepA-RBPBS to the target RNA data of RBPs related to diabetes (LIN28, RBFOX2, FTO, IGF2BP2, CELF1 and HuR). The results show that DeepA-RBPBS correctly predicted 41,693 samples, where iDeepS predicted 31,381 samples.Communicated by Ramaswamy H. Sarma.

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).

Targeting gut barrier dysfunction with phytotherapies: Effective strategy against chronic diseases

The intestinal epithelial layer serves as a physical and functional barrier between the microbe-rich lumen and immunologically active submucosa; it prevents systemic translocation of microbial pyrogenic products (e.g. endotoxin) that elicits immune activation upon translocation to the systemic circulation. Loss of barrier function has been associated with chronic 'low-grade' systemic inflammation which underlies pathogenesis of numerous no-communicable chronic inflammatory disease. Thus, targeting gut barrier dysfunction is an effective strategy for the prevention and/or treatment of chronic disease. This review intends to emphasize on the beneficial effects of herbal formulations, phytochemicals and traditional phytomedicines in attenuating intestinal barrier dysfunction. It also aims to provide a comprehensive understanding of intestinal-level events leading to a 'leaky-gut' and systemic complications mediated by endotoxemia. Additionally, a variety of detectable markers and diagnostic criteria utilized to evaluate barrier improving capacities of experimental therapeutics has been discussed. Collectively, this review provides rationale for targeting gut barrier dysfunction by phytotherapies for treating chronic diseases that are associated with endotoxemia-induced systemic inflammation.

Synbiotics Alter Fecal Microbiomes, But Not Liver Fat or Fibrosis, in a Randomized Trial of Patients With Nonalcoholic Fatty Liver Disease

BACKGROUND & AIMS

Dysbiosis of the intestinal microbiota has been associated with nonalcoholic fatty liver disease (NAFLD). We investigated whether administration of a synbiotic combination of probiotic and prebiotic agents affected liver fat content, biomarkers of liver fibrosis, and the composition of the fecal microbiome in patients with NAFLD.

METHODS

We performed a double-blind phase 2 trial of 104 patients with NAFLD in the United Kingdom. Participants (mean age, 50.8 ± 12.6 years; 65% men; 37% with diabetes) were randomly assigned to groups given the synbiotic agents (fructo-oligosaccharides, 4 g twice per day, plus Bifidobacterium animalis subspecies lactis BB-12; n = 55) or placebo (n = 49) for 10-14 months. Liver fat content was measured at the start and end of the study by magnetic resonance spectroscopy, and liver fibrosis was determined from a validated biomarker scoring system and vibration-controlled transient elastography. Fecal samples were collected at the start and end of the study, the fecal microbiome were analyzed by 16S ribosomal DNA sequencing.

RESULTS

Mean baseline and end-of-study magnetic resonance spectroscopy liver fat percentage values were 32.3% ± 24.8% and 28.5% ± 20.1% in the synbiotic group and 31.3% ± 22% and 25.2% ± 17.2% in the placebo group. In the unadjusted intention-to-treat analysis, we found no significant difference in liver fat reduction between groups (β = 2.8; 95% confidence interval, -2.2 to 7.8; P = .30). In a fully adjusted regression model (adjusted for baseline measurement of the outcome plus age, sex, weight difference, and baseline weight), only weight loss was associated with a significant decrease in liver fat (β = 2; 95% confidence interval, 1.5-2.6; P = .03). Fecal samples from patients who received the synbiotic had higher proportions of Bifidobacterium and Faecalibacterium species, and reductions in Oscillibacter and Alistipes species, compared with baseline; these changes were not observed in the placebo group. Changes in the composition of fecal microbiota were not associated with liver fat or markers of fibrosis.

CONCLUSIONS

In a randomized trial of patients with NAFLD, 1 year of administration of a synbiotic combination (probiotic and prebiotic) altered the fecal microbiome but did not reduce liver fat content or markers of liver fibrosis. (ClinicalTrials.gov, Number: NCT01680640).

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.

Intestinal permeability in the pathogenesis of liver damage: From non-alcoholic fatty liver disease to liver transplantation

The intimate connection and the strict mutual cooperation between the gut and the liver realizes a functional entity called gut-liver axis. The integrity of intestinal barrier is crucial for the maintenance of liver homeostasis. In this mutual relationship, the liver acts as a second firewall towards potentially harmful substances translocated from the gut, and is, in turn, is implicated in the regulation of the barrier. Increasing evidence has highlighted the relevance of increased intestinal permeability and consequent bacterial translocation in the development of liver damage. In particular, in patients with non-alcoholic fatty liver disease recent hypotheses are considering intestinal permeability impairment, diet and gut dysbiosis as the primary pathogenic trigger. In advanced liver disease, intestinal permeability is enhanced by portal hypertension. The clinical consequence is an increased bacterial translocation that further worsens liver damage. Furthermore, this pathogenic mechanism is implicated in most of liver cirrhosis complications, such as spontaneous bacterial peritonitis, hepatorenal syndrome, portal vein thrombosis, hepatic encephalopathy, and hepatocellular carcinoma. After liver transplantation, the decrease in portal pressure should determine beneficial effects on the gut-liver axis, although are incompletely understood data on the modifications of the intestinal permeability and gut microbiota composition are still lacking. How the modulation of the intestinal permeability could prevent the initiation and progression of liver disease is still an uncovered area, which deserves further attention.

Platelet number in different anticoagulants as a diagnostic biomarker for increased intestinal permeability

The main pathological process associated to increased intestinal permeability is the translocation of toxic products, predominantly endotoxins/lipopolysaccharide (LPS), from the intestinal tract into the microcirculation. In blood, LPS binds to surface receptors on immune cells initiating an inflammatory response. LPS can also bind to platelets leading to preactivated platelets that have a lower threshold to be aggregated in presence heparin. The aim of this study was to validate a simple, fast and reliable test for screening LPS-loaded platelets. This test named PANDA (acronym for Platelet Number in Different Anticoagulants) consists in the measurement of the mean platelet number in blood samples collected into EDTA and heparin. We analyzed blood samples from 92 patients with gastrointestinal diseases and 23 healthy volunteers and found a markedly low number of platelets in heparinized blood compared to EDTA-anticoagulated blood in patients but not in healthy volunteers. Furthermore, ex vivo addition of endotoxin to blood samples induced a remarkable decrease in platelet count in heparinized blood of the volunteers but not in the patient's group, where platelets could be previously saturated by endotoxin circulating in blood. Platelet should be counted during the first hour after blood collection, in order to avoid false results due to a progressive platelet aggregation in heparinized blood in function of the time. Our results demonstrated that PANDA test can be used for screening LPS-loaded platelets as an indirect diagnostic biomarker for increased intestinal permeability and also for monitoring the gut barrier function during the treatment of gastrointestinal diseases.

Treatment Interventions for the Management of Intestinal Permeability: A Cross-Sectional Survey of Complementary and Integrative Medicine Practitioners

Objectives: This study aims to explore the treatment interventions complementary and integrative medicine (CIM) practitioners use in the management of an emerging health condition, increased intestinal permeability (IP), and the association these methods have on the observed time to resolve this condition. Design and setting: A cross-sectional survey of Australian naturopaths, nutritionists, and Western herbal medicine practitioners was undertaken (n = 227) through the Practitioner Research and Collaboration Initiative (PRACI) network. Outcome measures: Frequencies and percentages of the treatment methods, including chi-square analysis to examine the associations between treatment methods and observed time to resolve IP. Results: Thirty-six CIM practitioners responded to the survey (response rate 15.9%). CIM practitioners were found to use a multimodal approach in the management of IP with 92.6% of respondents using three or more categories of treatment interventions (nutritional, herbal, dietary, and lifestyle) with a mean total of 43.0 ± 24.89 single treatment interventions frequently prescribed. The main treatments prescribed in the management of IP were zinc (85.2%), probiotics: multistrain (77.8%), vitamin D (75.0%), glutamine (73.1%), Curcuma longa (73.1%), and Saccharomyces boulardii (70.4%). CIM practitioners also advocate patients with IP to reduce alcohol (96.3%), gluten (85.2%), and dairy (75.0%) consumption. Evaluation of antibiotics (75.0%) and nonsteroidal anti-inflammatory drugs (73.1%) prescriptions were frequently advised by CIM practitioners. A longer observed time to resolve IP was seen in CIM practitioners who did not reduce intense exercise in the management of IP (p = 0.02). Conclusions: This study represents the first survey of the treatments prescribed by CIM practitioners for IP and suggests that CIM practitioners use numerous integrative treatment methods for the management of IP. The treatment interventions frequently prescribed by CIM practitioners align with preclinical research, suggesting that CIM practitioners prescribe in accordance with the published literature. The findings of this study contribute to the implementation of clinical research in the management of IP, which considers multiple concurrent treatments.

Intraindividual Variation in Markers of Intestinal Permeability and Adipose Tissue Inflammation in Healthy Normal-Weight to Obese Adults

BACKGROUND

Intestinal permeability and adipose tissue inflammation are considered mechanistic links in the relationship between diet, obesity, and chronic disease. However, methods to measure both are not well standardized, and the reliability of commonly used measures is not known.

METHODS

We calculated the intraclass correlation coefficient (ICC) for several common measures of intestinal permeability and adipose tissue inflammation from a randomized clinical trial of cross-over design in which normal-weight (n = 12) or overweight/obese (n = 12) individuals each completed three 8-day dietary intervention periods.

RESULTS

For biomarkers of intestinal permeability, plasma zonulin, and lipopolysaccharide-binding protein, ICCs were "excellent" (i.e., >0.9). The direct measure of intestinal permeability, the lactulose/mannitol test, exhibited "fair" reliability (ICC = 0.53). A wider range of ICCs (0.6-0.9), suggesting "good" to "excellent" reliability, were obtained for measures of adipose tissue expression of genes encoding major mediators of inflammation. Similarly, individual immune cell populations isolated from adipose tissue, expressed as a percentage of all CD45⁺ cells, also had "good" to "excellent" ICCs. However, when these populations were expressed as number of cells per gram of tissue, ICC values were "fair," falling below 0.6.

CONCLUSIONS

Due to the repeated measures design, our study offered a unique opportunity to assess reliability of commonly used biomarkers of intestinal permeability and adipose tissue inflammation. Our findings suggest that these measures were generally highly reliable in the short-term.

IMPACT

Along with other factors, particularly validity, the demonstrated reliabilities can help inform the choice of endpoints in studies of intestinal permeability and adipose tissue inflammation.

Bacterial translocation in patients with liver cirrhosis: physiology, clinical consequences, and practical implications

The gut liver axis is an operative unit that works to protect the human body against potentially harmful substances and microorganisms, maintaining the homeostasis of the immune system. Liver cirrhosis profoundly alters this complex system. The intestine becomes more permeable allowing the translocation of bacteria, bacterial products and fragments into the portal circulation, triggering an abnormal local and systemic inflammatory response and a condition of perpetual immunologic alarm. This immune-inflammatory disorder related to dysbiosis is involved in the development of liver damage and liver cirrhosis complications and increases intestinal permeability in a vicious circle. Areas covered: The most relevant studies on bacterial translocation, the mechanism of intestinal barrier dysfunction and its consequences in patients with liver cirrhosis have been revised through a PubMed search. Data have been discussed with particular regard to their significance in clinical practice. Expert commentary: The assessment of bacterial translocation and intestinal permeability is not currently used in clinical practice but may be useful to stratify patients' prognosis.

Characterizing the Biochemical Response to Schistosoma mansoni Infection and Treatment with Praziquantel in Preschool and School Aged Children

Schistosomiasis is a widespread chronic neglected tropical disease prevalent mostly in children in under-resourced rural areas. Its pathological effects have been clinically characterized, yet the molecular-level effects are understudied. In this study, the biochemical effects of Schistosoma mansoni infection and praziquantel treatment were studied in 130 preschool aged and 159 school aged infected children and 11 noninfected children in Azaguié, Côte d'Ivoire. Urine samples were collected prior to receiving 20, 40, or 60 mg/kg of praziquantel or a placebo, as well as 24 h post-treatment, and at the 3-week follow up. Urinary metabolic phenotypes were measured using ¹H NMR spectroscopy, and metabolic variation associated with S. mansoni infection and praziquantel administration was identified using multivariate statistical techniques. Discriminatory metabolic signatures were detected between heavily infected and noninfected children at baseline as well as according to the dose of praziquantel administered 24 h post treatment. These signatures were primarily associated with the metabolic activity of the gut microbiota, gut health and growth biomarkers and energy and liver metabolism. These analyses provide insights into the metabolic phenotype of schistosomiasis and treatment with praziquantel in two important demographics.

Rhubarb Monomers Protect Intestinal Mucosal Barrier in Sepsis via Junction Proteins

Background:

Leakage of the intestinal mucosal barrier may cause translocation of bacteria, then leading to multiorgan failure. This study hypothesized that rhubarb monomers might protect the gut mucosal barrier in sepsis through junction proteins.

Methods:

Healthy male Sprague-Dawley rats (weighing 230–250 g) under anesthesia and sedation were subjected to cecal ligation and perforation (CLP). After surgical preparation, rats were randomly assigned to eight groups (n = 6 or 8 each group): sham group (Group A: normal saline gavage); sepsis group (Group B: normal saline gavage); Group C (intraperitoneally, dexamethasone 0.5 mg/kg) immediately after CLP surgery; and rhubarb monomer (100 mg/kg in normal saline)-treated groups (Group D: rhein; Group E: emodin; Group F: 3,8-dihydroxy-1-methyl-anthraquinone-2-carboxylic acid; Group G: 1-O-caffeoyl-2-(4-hydroxy-O-cinnamoyl)-D-glucose; and Group H: daucosterol linoleate). Animals were sacrificed after 24 h. Intestinal histology, lactulose, mannitol concentrations were measured, and zonula occludens (ZO)-1, occludin and claudin-5 transcription (polymerase chain reaction), translation (by Western blot analysis), and expression (by immunohistochemistry) were also measured.

Results:

Intestinal histology revealed injury to intestinal mucosal villi induced by sepsis in Group B, compared with Group A. Compared with Group A (0.17 ± 0.41), the pathological scores in Groups B (2.83 ± 0.41, P < 0.001), C (1.83 ± 0.41, P < 0.001), D (2.00 ± 0.63, P < 0.001), E (1.83 ± 0.41, P < 0.001), F (1.83 ± 0.75, P < 0.001), G (2.17 ± 0.41, P < 0.001), and H (1.83 ± 0.41, P < 0.001) were significantly increased. Lactulose/mannitol (L/M) ratio in Group B (0.046 ± 0.003) was significantly higher than in Group A (0.013 ± 0.001, P < 0.001) while L/M ratios in Groups C (0.028 ± 0.002, P < 0.001), D (0.029 ± 0.003, P < 0.001), E (0.026 ± 0.003, P < 0.001), F (0.027 ± 0.003, P < 0.001), G (0.030 ± 0.005, P < 0.001), and H (0.026 ± 0.002, P < 0.001) were significantly lower than that in Group B. ZO-1, occludin and claudin-5 transcription, translation, and expression in Group B were significantly lower than that in Group A (P < 0.001), but they were significantly higher in Groups C, D, E, F, G, and H than those in Group B (P < 0.05).

Conclusion:

Rhubarb monomer treatment ameliorated mucosal damage in sepsis via enhanced transcription, translation, and expression of junction proteins.

The effects of a multispecies probiotic on migraine and markers of intestinal permeability-results of a randomized placebo-controlled study

BACKGROUND/OBJECTIVES

Migraine, associated with several gastrointestinal disorders, may result from increased intestinal permeability, allowing endotoxins to enter the bloodstream. We tested whether probiotics could reduce migraine through an effect on intestinal permeability and inflammation.

SUBJECTS/METHODS

In total, 63 patients were randomly allocated to the probiotic (n=31) or the placebo group (n=32). Participants ingested a multispecies probiotic (5x10⁹ colony-forming units) or placebo daily for 12 weeks. Migraine was assessed with the Migraine Disability Assessment Scale (MIDAS), the Headache Disability Inventory (HDI) and headache diaries. At baseline and 12 weeks, intestinal permeability was measured with the urinary lactulose/mannitol test and fecal and serum zonulin; inflammation was measured from interleukin (IL) -6, IL-10, tumor necrosis factor-α and C-reactive protein in serum.

RESULTS

The MIDAS migraine intensity score significantly decreased in both groups (P<0.001) and the HDI score significantly decreased in the probiotic group (P=0.032) and borderline in the placebo group (P=0.053). In the probiotics group, patients had a median of 6 migraine days in the first month, 4 in the second month (P=0.002) and 5 in the last month, which was not significantly different from the 5, 4, and 4 days in the placebo group. A ⩾2day reduction in migraine days was seen in 12/31 patients in the probiotics group versus 7/29 in the placebo group (ns). Probiotic use did not significantly affect medication use, intestinal permeability or inflammation compared to placebo.

CONCLUSIONS

In this study, we could not confirm significant benefit from a multispecies probiotic compared to a placebo on the outcome parameters of migraine and intestinal integrity.

NMR-based urinary profiling of lactulose/mannitol ratio used to assess the altered intestinal permeability in acute on chronic liver failure (ACLF) patients

The article presents a simplified NMR-based protocol for urinary profiling of lactulose/mannitol ratio (LMR) and demonstrates here its utility to assess increased intestinal permeability (IP) in patients with acute on chronic liver failure (ACLF). ACLF is a serious clinical complication associated with chronic liver disease (cirrhosis). The major risk factor in its development is increased IP ('leaky gut'), which has been linked to disease progression and to infectious complications. However, IP has seldom been investigated in patients with ACLF, even though patients frequently report gastrointestinal disorders and associated complications. To this end, we first optimized the NMR-based targeted profiling of urinary metabolites (i.e. actulose, mannitol, and creatinine) and subsequently used this resulted protocol (a) first to evaluate the altered IP in ACLF patients and then (b) to explore its utility for monitoring the treatment response in these patients. The normal profiles were obtained for 7 age and sex matched healthy volunteers. The results revealed that the urinary LMR excretion was significantly higher in ACLF patients compared to normal controls (median ~0.7, range (0.12-2.84), vs median ~0.11, range (0.02-0.28), p < 0.001) suggesting that the ACLF patients' exhibit altered IP. However, the LMR excretion in six clinically improved follow-up ACLF patients was comparable to normal controls indicating restored IP after the treatment. The protocol-as demonstrated here with ACLF-is equally applicable for evaluating IP or mucosal barrier function in other intestinal disorders with reasonable sensitivity and specificity, highlighting its general utility. Copyright © 2016 John Wiley & Sons, Ltd.

Intestinal permeability in a patient with liver cirrhosis

Liver cirrhosis is a worldwide public health problem, and patients with this disease are at high risk of developing complications, bacterial translocation from the intestinal lumen to the mesenteric nodes, and systemic circulation, resulting in the development of severe complications related to high mortality rate. The intestinal barrier is a structure with a physical and biochemical activity to maintain balance between the external environment, including bacteria and their products, and the internal environment. Patients with liver cirrhosis develop a series of alterations in different components of the intestinal barrier directly associated with the severity of liver disease that finally increased intestinal permeability. A "leaky gut" is an effect produced by damaged intestinal barrier; alterations in the function of tight junction proteins are related to bacterial translocation and their products. Instead, increasing serum proinflammatory cytokines and hemodynamics modification, which results in the appearance of complications of liver cirrhosis such as hepatic encephalopathy, variceal hemorrhage, bacterial spontaneous peritonitis, and hepatorenal syndrome. The intestinal microbiota plays a fundamental role in maintaining the proper function of the intestinal barrier; bacterial overgrowth and dysbiosis are two phenomena often present in people with liver cirrhosis favoring bacterial translocation. Increased intestinal permeability has an important role in the genesis of these complications, and treating it could be the base for prevention and partial treatment of these complications.

No differential effect of beverages sweetened with fructose, high-fructose corn syrup, or glucose on systemic or adipose tissue inflammation in normal-weight to obese adults: a randomized controlled trial

BACKGROUND

Sugar-sweetened beverage (SSB) consumption and low-grade chronic inflammation are both independently associated with type 2 diabetes and cardiovascular disease. Fructose, a major component of SSBs, may acutely trigger inflammation, which may be one link between SSB consumption and cardiometabolic disease.

OBJECTIVE

We sought to determine whether beverages sweetened with fructose, high-fructose corn syrup (HFCS), and glucose differentially influence systemic inflammation [fasting plasma C-reactive protein and interleukin-6 (IL-6) as primary endpoints] acutely and before major changes in body weight. Secondary endpoints included adipose tissue inflammation, intestinal permeability, and plasma fetuin-A as potential mechanistic links between fructose intake and low-grade inflammation.

DESIGN

We conducted a randomized, controlled, double-blind, crossover design dietary intervention (the Diet and Systemic Inflammation Study) in 24 normal-weight to obese adults without fructose malabsorption. Participants drank 4 servings/d of fructose-, glucose-, or HFCS-sweetened beverages accounting for 25% of estimated calorie requirements while consuming a standardized diet ad libitum for three 8-d periods.

RESULTS

Subjects consumed 116% of their estimated calorie requirement while drinking the beverages with no difference in total energy intake or body weight between groups as reported previously. Fasting plasma concentrations of C-reactive protein and IL-6 did not differ significantly at the end of the 3 diet periods. We did not detect a consistent differential effect of the diets on measures of adipose tissue inflammation except for adiponectin gene expression in adipose tissue (P = 0.005), which was lowest after the glucose phase. We also did not detect consistent evidence of a differential impact of these sugars on measures of intestinal permeability (lactulose:mannitol test, plasma zonulin, and plasma lipopolysaccharide-binding protein).

CONCLUSION

Excessive amounts of fructose, HFCS, and glucose from SSBs consumed over 8 d did not differentially affect low-grade chronic systemic inflammation in normal-weight to obese adults. This trial was registered at clinicaltrials.gov as NCT01424306.

A method for assessing real time rates of dissolution and absorption of carbohydrate and other food matrices in human subjects

We prepared pasta of differing physical dimensions but identical chemical composition that contained two monosaccharide probes (lactulose and mannitol) that are absorbed passively and promptly excreted in urine. We showed that the rates of their liberation from the pasta under simulated gastric and small intestinal conditions largely depended upon the rate of digestion of the starchy matrix. We showed, in 20 female subjects, that excretion of mannitol was slower from the pasta with the larger particle size. Hence, after consumption of either the powdered pasta or the simple solution of probe sugars, the mass of mannitol excreted between 1 and 2½ hours was greater than that excreted between 2½ and 4 hours. However these masses did not differ significantly after consumption of the pasta pellets. These differences were not reflected in the concurrent patterns of variation in either serum glucose or insulin taken over 120 minutes, their levels being similar for pasta pellets and powder with their peak values occurring synchronously during the first hour. Hence feeding test foods impregnated with lactulose and mannitol probes provided a reproducible and practical means of assessing the timing of digestion of the carbohydrate matrix and showed that this was more protracted than suggested by post prandial glucose levels. Further, the transit times calculated on a basis of the ratios of the two marker sugars could identify that the prolongation of digestion of larger particles was not accompanied by retention of digesta in particular segments of the gut.

Changes of Intestinal Functions in Liver Cirrhosis

Background

Understanding of the gut-liver axis is important for the up-to-date management of liver cirrhosis, and changes of intestinal functions form the core of this interesting research field.

Summary

Most investigators noted small intestinal dysmotility in their patients with liver cirrhosis. Marked changes in the contraction pattern were observed in early manometric studies. The orocecal transit time, particularly small intestinal transit, has generally been reported to be prolonged, which has been demonstrated in multiple investigations to be related to the severity of the liver disease (e.g., Child-Pugh class), the presence of small intestinal bacterial overgrowth (SIBO) and hepatic encephalopathy (HE) as well as a history of spontaneous bacterial peritonitis. Bacteriologically proven SIBO in proximal jejunal aspiration has been reported to be present in up to 59% of cirrhotic patients and is associated with systemic endotoxemia. Clinical and experimental studies suggest that delayed small bowel transit in liver cirrhosis may lead to SIBO, which could contribute to the symptoms of abdominal pain and diarrhea. In addition to autonomic neuropathy, metabolic derangements and diabetic state, SIBO itself may delay intestinal transit in cirrhotic patients. Several studies, both from the West and the East, have shown that the gut microbiota is altered in cirrhotic patients and particularly those with HE. Further, a quantitative change in Bacteroides/Firmicutes ratio, with a prevalence of potentially pathogenic bacteria (e.g., Enterobacteriaceae) and reduction in specific commensals (e.g., Lachnospiraceae), has been described. Structural and functional changes in the intestinal mucosa that contribute to increases in intestinal permeability for bacteria and their products have been observed in patients with liver cirrhosis, which is considered as an important pathogenetic factor for several complications. The mechanism of intestinal barrier dysfunction in cirrhosis is multifactorial, including alcohol, portal hypertension (vascular congestion and dysregulation), endotoxemia, SIBO, local inflammation and, most likely, immunological factors and medications.

Key Messages

This review summarizes major achievements regarding intestinal dysfunction in cirrhosis for future gastroenterology research. The question of whether this intestinal barrier dysfunction is accompanied and/or at least partly caused by structural and functional changes in the epithelial tight junction proteins is as yet unsolved. Development of new strategies to modulate gut-liver interaction is urgently needed.

Changes of Intestinal Functions in Liver Cirrhosis

BACKGROUND

Understanding of the gut-liver axis is important for the up-to-date management of liver cirrhosis, and changes of intestinal functions form the core of this interesting research field.

SUMMARY

Most investigators noted small intestinal dysmotility in their patients with liver cirrhosis. Marked changes in the contraction pattern were observed in early manometric studies. The orocecal transit time, particularly small intestinal transit, has generally been reported to be prolonged, which has been demonstrated in multiple investigations to be related to the severity of the liver disease (e.g., Child-Pugh class), the presence of small intestinal bacterial overgrowth (SIBO) and hepatic encephalopathy (HE) as well as a history of spontaneous bacterial peritonitis. Bacteriologically proven SIBO in proximal jejunal aspiration has been reported to be present in up to 59% of cirrhotic patients and is associated with systemic endotoxemia. Clinical and experimental studies suggest that delayed small bowel transit in liver cirrhosis may lead to SIBO, which could contribute to the symptoms of abdominal pain and diarrhea. In addition to autonomic neuropathy, metabolic derangements and diabetic state, SIBO itself may delay intestinal transit in cirrhotic patients. Several studies, both from the West and the East, have shown that the gut microbiota is altered in cirrhotic patients and particularly those with HE. Further, a quantitative change in Bacteroides/Firmicutes ratio, with a prevalence of potentially pathogenic bacteria (e.g., Enterobacteriaceae) and reduction in specific commensals (e.g., Lachnospiraceae), has been described. Structural and functional changes in the intestinal mucosa that contribute to increases in intestinal permeability for bacteria and their products have been observed in patients with liver cirrhosis, which is considered as an important pathogenetic factor for several complications. The mechanism of intestinal barrier dysfunction in cirrhosis is multifactorial, including alcohol, portal hypertension (vascular congestion and dysregulation), endotoxemia, SIBO, local inflammation and, most likely, immunological factors and medications.

KEY MESSAGES

This review summarizes major achievements regarding intestinal dysfunction in cirrhosis for future gastroenterology research. The question of whether this intestinal barrier dysfunction is accompanied and/or at least partly caused by structural and functional changes in the epithelial tight junction proteins is as yet unsolved. Development of new strategies to modulate gut-liver interaction is urgently needed.

Changes of Intestinal Functions in Liver Cirrhosis

Background

Understanding of the gut-liver axis is important for the up-to-date management of liver cirrhosis, and changes of intestinal functions form the core of this interesting research field.

Summary

Most investigators noted small intestinal dysmotility in their patients with liver cirrhosis. Marked changes in the contraction pattern were observed in early manometric studies. The orocecal transit time, particularly small intestinal transit, has generally been reported to be prolonged, which has been demonstrated in multiple investigations to be related to the severity of the liver disease (e.g., Child-Pugh class), the presence of small intestinal bacterial overgrowth (SIBO) and hepatic encephalopathy (HE) as well as a history of spontaneous bacterial peritonitis. Bacteriologically proven SIBO in proximal jejunal aspiration has been reported to be present in up to 59% of cirrhotic patients and is associated with systemic endotoxemia. Clinical and experimental studies suggest that delayed small bowel transit in liver cirrhosis may lead to SIBO, which could contribute to the symptoms of abdominal pain and diarrhea. In addition to autonomic neuropathy, metabolic derangements and diabetic state, SIBO itself may delay intestinal transit in cirrhotic patients. Several studies, both from the West and the East, have shown that the gut microbiota is altered in cirrhotic patients and particularly those with HE. Further, a quantitative change in Bacteroides/Firmicutes ratio, with a prevalence of potentially pathogenic bacteria (e.g., Enterobacteriaceae) and reduction in specific commensals (e.g., Lachnospiraceae), has been described. Structural and functional changes in the intestinal mucosa that contribute to increases in intestinal permeability for bacteria and their products have been observed in patients with liver cirrhosis, which is considered as an important pathogenetic factor for several complications. The mechanism of intestinal barrier dysfunction in cirrhosis is multifactorial, including alcohol, portal hypertension (vascular congestion and dysregulation), endotoxemia, SIBO, local inflammation and, most likely, immunological factors and medications.

Key Messages

This review summarizes major achievements regarding intestinal dysfunction in cirrhosis for future gastroenterology research. The question of whether this intestinal barrier dysfunction is accompanied and/or at least partly caused by structural and functional changes in the epithelial tight junction proteins is as yet unsolved. Development of new strategies to modulate gut-liver interaction is urgently needed.

The effect of prebiotic supplementation with inulin on cardiometabolic health: Rationale, design, and methods of a controlled feeding efficacy trial in adults at risk of type 2 diabetes

Prediabetes is associated with low-grade chronic inflammation that increases the risk for developing type 2 diabetes (T2D) and cardiovascular disease (CVD). An elevated lipopolysaccharide concentration, associated with dysbiosis of the intestinal microbiota, has been implicated in the development of both T2D and CVD. Selective modulation of the intestinal microbiota with prebiotics reduces intestinal permeability and endotoxin concentrations, inflammation, and metabolic dysfunction in rodents. The effect of prebiotic supplementation on cardio-metabolic function in humans at risk for T2D is not known. The primary aim of this trial is to determine the influence of prebiotic supplementation with inulin on insulin sensitivity and skeletal muscle metabolic flexibility in adults at risk for T2D. We hypothesize that prebiotic supplementation with inulin will improve insulin sensitivity and skeletal muscle metabolic flexibility. We will randomize 48 adults (40-75 yrs) with prediabetes or a score ≥ 5 on the American Diabetes Association (ADA) risk screener to 6 weeks of prebiotic supplementation with inulin (10 g/day) or placebo. Subjects will be provided with all food for the duration of the study, to avoid potential confounding through differences in dietary intake between individuals. Intestinal permeability, serum endotoxin concentrations, insulin sensitivity, skeletal muscle metabolic flexibility, endothelial function, arterial stiffness, and fecal bacterial composition will be measured at baseline and following treatment. The identification of prebiotic supplementation with inulin as an efficacious strategy for reducing cardio-metabolic risk in individuals at risk of T2D could impact clinical practice by informing dietary recommendations and increasing acceptance of prebiotics by the scientific and medical community.

Urinary Sugars--A Biomarker of Total Sugars Intake

Measurement error in self-reported sugars intake may explain the lack of consistency in the epidemiologic evidence on the association between sugars and disease risk. This review describes the development and applications of a biomarker of sugars intake, informs its future use and recommends directions for future research. Recently, 24 h urinary sucrose and fructose were suggested as a predictive biomarker for total sugars intake, based on findings from three highly controlled feeding studies conducted in the United Kingdom. From this work, a calibration equation for the biomarker that provides an unbiased measure of sugars intake was generated that has since been used in two US-based studies with free-living individuals to assess measurement error in dietary self-reports and to develop regression calibration equations that could be used in future diet-disease analyses. Further applications of the biomarker include its use as a surrogate measure of intake in diet-disease association studies. Although this biomarker has great potential and exhibits favorable characteristics, available data come from a few controlled studies with limited sample sizes conducted in the UK. Larger feeding studies conducted in different populations are needed to further explore biomarker characteristics and stability of its biases, compare its performance, and generate a unique, or population-specific biomarker calibration equations to be applied in future studies. A validated sugars biomarker is critical for informed interpretation of sugars-disease association studies.

Methods to determine intestinal permeability and bacterial translocation during liver disease

Liver disease is often times associated with increased intestinal permeability. A disruption of the gut barrier allows microbial products and viable bacteria to translocate from the intestinal lumen to extraintestinal organs. The majority of the venous blood from the intestinal tract is drained into the portal circulation, which is part of the dual hepatic blood supply. The liver is therefore the first organ in the body to encounter not only absorbed nutrients, but also gut-derived bacteria and pathogen associated molecular patterns (PAMPs). Chronic exposure to increased levels of PAMPs has been linked to disease progression during early stages and to infectious complications during late stages of liver disease (cirrhosis). It is therefore important to assess and monitor gut barrier dysfunction during hepatic disease. We review methods to assess intestinal barrier disruption and discuss advantages and disadvantages. We will in particular focus on methods that we have used to measure increased intestinal permeability and bacterial translocation in experimental liver disease models.

JAK2 and AMP-kinase inhibition in vitro by food extracts, fractions and purified phytochemicals

A study of 49 foods shows that ellagitannin containing foods inhibit JAK2 and AMPK kinases.

A 12 week longitudinal study of microbial translocation and systemic inflammation in undernourished HIV-infected Zambians initiating antiretroviral therapy

Background

Undernourished, HIV-infected adults in sub-Saharan Africa have high levels of systemic inflammation, which is a risk factor for mortality and other adverse health outcomes. We hypothesized that microbial translocation, due to the deleterious effects of HIV and poor nutrition on intestinal defenses and mucosal integrity, contributes to heightened systemic inflammation in this population, and reductions in inflammation on antiretroviral therapy (ART) accompany reductions in translocation.

Methods

HIV-infected, Zambian adults with a body mass index <18.5 kg/m² were recruited for a pilot study to assess the relationships between microbial translocation and systemic inflammation over the first 12 weeks of ART. To assess microbial translocation we measured serum lipopolysaccharide binding protein (LBP), endotoxin core IgG and IgM, and soluble CD14, and to assess intestinal permeability we measured the urinary excretion of an oral lactulose dose normalized to urinary creatinine (Lac/Cr ratio). Linear mixed models were used to assess within-patient changes in these markers relative to serum C-reactive protein (CRP), tumor necrosis factor-α receptor 1 (TNF-α R1), and soluble CD163 over 12 weeks, in addition to relationships between variables independent of time point and adjusted for age, sex, and CD4+ count.

Results

Thirty-three participants had data from recruitment and at 12 weeks: 55% were male, median age was 36 years, and median baseline CD4+ count was 224 cells/μl. Over the first 12 weeks of ART, there were significant decreases in serum levels of LBP (median change -8.7 μg/ml, p = 0.01), TNF-α receptor 1 (-0.31 ng/ml, p < 0.01), and CRP (-3.5 mg/l, p = 0.02). The change in soluble CD14 level over 12 weeks was positively associated with the change in CRP (p < 0.01) and soluble CD163 (p < 0.01). Pooling data at baseline and 12 weeks, serum LBP was positively associated with CRP (p = 0.01), while endotoxin core IgM was inversely associated with CRP (p = 0.01) and TNF-α receptor 1 (p = 0.04). The Lac/Cr ratio was not associated with any serum biomarkers.

Conclusions

In undernourished HIV-infected adults in Zambia, biomarkers of increased microbial translocation are associated with high levels of systemic inflammation before and after initiation of ART, suggesting that impaired gut immune defenses contribute to innate immune activation in this population.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2334-14-521) contains supplementary material, which is available to authorized users.

Standardising the lactulose mannitol test of gut permeability to minimise error and promote comparability

BACKGROUND

Lactulose mannitol ratio tests are clinically useful for assessing disorders characterised by changes in gut permeability and for assessing mixing in the intestinal lumen. Variations between currently used test protocols preclude meaningful comparisons between studies. We determined the optimal sampling period and related this to intestinal residence.

METHODS

Half-hourly lactulose and mannitol urinary excretions were determined over 6 hours in 40 healthy female volunteers after administration of either 600 mg aspirin or placebo, in randomised order at weekly intervals. Gastric and small intestinal transit times were assessed by the SmartPill in 6 subjects from the same population. Half-hourly percentage recoveries of lactulose and mannitol were grouped on a basis of compartment transit time. The rate of increase or decrease of each sugar within each group was explored by simple linear regression to assess the optimal period of sampling.

KEY RESULTS

The between subject standard errors for each half-hourly lactulose and mannitol excretion were lowest, the correlation of the quantity of each sugar excreted with time was optimal and the difference between the two sugars in this temporal relationship maximal during the period from 2½-4 h after ingestion. Half-hourly lactulose excretions were generally increased after dosage with aspirin whilst those of mannitol were unchanged as was the temporal pattern and period of lowest between subject standard error for both sugars.

CONCLUSION

The results indicate that between subject variation in the percentage excretion of the two sugars would be minimised and the differences in the temporal patterns of excretion would be maximised if the period of collection of urine used in clinical tests of small intestinal permeability were restricted to 2½-4 h post dosage. This period corresponds to a period when the column of digesta column containing the probes is passing from the small to the large intestine.

Intestinal permeability is increased in children with non-alcoholic fatty liver disease, and correlates with liver disease severity

BACKGROUND

Increased intestinal permeability seems to play a major role in non-alcoholic liver disease development and progression.

AIM

To investigate the prevalence of altered intestinal permeability in children with non-alcoholic fatty liver disease, and to study its potential association with the stage of liver disease.

METHODS

We performed a case-control study examining intestinal permeability in children using the lactulose-mannitol bowel permeability test.

RESULTS

Overall, 39 consecutive patients (30 males, median age 12 years) and 21 controls (14 males, median age 11.8 years) were included. The lactulose/mannitol ratio resulted impaired in 12/39 patients (31%) and none of the controls. Intestinal permeability was higher in children with non-alcoholic fatty liver disease (lactulose/mannitol ratios: 0.038±0.037 vs. 0.008±0.007, p<0.05). Within the non-alcoholic fatty liver disease group, intestinal permeability was increased in children with steatohepatitis compared to those with steatosis only (0.05±0.04 vs. 0.03 vs. 0.03, p<0.05). Pathological lactulose/mannitol ratio correlated with portal inflammation (p=0.02), fibrosis (p=0.0002), and ballooning of hepatocytes (p=0.003). Blood lipopolysaccharides levels were higher in children with steatohepatitis (2.27±0.68 vs. 2.80±0.35, p<0.05).

CONCLUSIONS

Intestinal permeability is increased in children with non-alcoholic fatty liver disease, and correlates with the severity of the disease.

Nutrition status and intestinal permeability in patients eligible for liver transplantation

BACKGROUND

Increased intestinal permeability has been reported in multiple studies of cirrhotic patients, although specific factors associated with this finding have not been fully elucidated. Thus, the aim of this study was to investigate whether there was an association between nutrition status measured by different methods and intestinal permeability in cirrhotic patients who were candidates for liver transplantation.

MATERIALS AND METHODS

The study group comprised 18 cirrhotic patients and 15 healthy controls. Patients' nutrition status was evaluated by Subjective Global Assessment (SGA), anthropometry, dynamometry, and phase angle, which was determined by bioelectrical impedance analysis. Intestinal permeability was assessed by the lactulose/mannitol test.

RESULTS

The prevalence of malnutrition showed wide variance between different assessment methods (5.5%-77.8%). Intestinal permeability was significantly higher in cirrhotic patients than in healthy controls. In relation to nutrition status, intestinal permeability and phase angle did not differ significantly between patients who were considered well nourished (median intestinal permeability, 0.010 [range, 0.001-0.198]; median phase angle, 6.0 [range, 4.2-6.9]) and malnourished patients (intestinal permeability, 0.032 [range, 0.002-0.079]; phase angle, 4.8 [range, 2.2-6.1]) by SGA. In addition, no correlation was found between nutrition diagnosis as assessed by different methods, patient age, liver disease severity scores, and laboratory measurements with intestinal permeability.

CONCLUSION

Although intestinal permeability was increased in cirrhotic patients, this finding was not associated with nutrition status.

Intestinal epithelial barrier function in liver cirrhosis: an extensive review of the literature

Recent evidence suggests that translocation of bacteria and bacterial products, such as endotoxin from the intestinal lumen into the systemic circulation is a contributing factor in the pathogenesis of chronic liver diseases and the development of complications in cirrhosis. In addition to alterations in the intestinal microbiota and immune system, dysfunction of the intestinal epithelial barrier may be an important factor facilitating bacterial translocation. This review aims to provide an overview of the current evidence of intestinal epithelial barrier dysfunction in human chronic liver diseases and cirrhosis, and to discuss possible contributing factors and mechanisms. Data suggest the presence of intestinal epithelial barrier dysfunction in patients with chronic liver diseases, but are more convincing in patients with cirrhosis, especially in those with complications. The barrier dysfunction can result from both direct and indirect effects of aetiological factors, such as alcohol and obesity, which can cause chronic liver diseases and ultimately cirrhosis. On the other hand characteristics of cirrhosis itself, including portal hypertension, alterations in the intestinal microbiota, inflammation and oxidative stress can affect barrier function of both small and large intestine and may contribute to the development of complications. In conclusion, there are indications for intestinal epithelial barrier dysfunction in patients with chronic liver diseases and especially in patients with cirrhosis, which can be caused by various factors affecting both the small and large intestine.

Symbiotic formulation in experimentally induced liver fibrosis in rats: intestinal microbiota as a key point to treat liver damage?

AIM

Evidence indicates that intestinal microbiota may participate in both the induction and the progression of liver damage. The aim of our research was the detection and evaluation of the effects of chronic treatment with a symbiotic formulation on CCl4 -induced rat liver fibrosis.

RESULTS

CCl4 significantly increased gastric permeability in respect to basal values, and the treatment with symbiotic significantly decreased it. CCl4 per se induced a decrease in intestinal permeability. This effect was also seen in fibrotic rats treated with symbiotic and was still evident when normal rats were treated with symbiotic alone (P < 0.001 in all cases). Circulating levels of pro-inflammatory cytokine TNF-α were significantly increased in rats with liver fibrosis as compared with normal rats, while symbiotic treatment normalized the plasma levels of TNF-α and significantly enhanced anti-inflammatory cytokine IL 10. TNF-α, TGF-β, TLR4, TLR2, iNOS and α-SMA mRNA expression in the liver were up-regulated in rats with CCl4 -induced liver fibrosis and down-regulated by symbiotic treatment. Moreover, IL-10 and eNOS mRNA levels were increased in the CCL4 (+) symbiotic group. Symbiotic treatment of fibrotic rats normalized serum ALT, AST and improved histology and liver collagen deposition. DGGE analysis of faecal samples revealed that CCl4 administration and symbiotic treatment either alone or in combination produced modifications in faecal profiles vs controls.

CONCLUSIONS

Our results provide evidence that in CCl4 -induced liver fibrosis, significant changes in gastro-intestinal permeability and in faecal flora occur. Treatment with a specific symbiotic formulation significantly affects these changes, leading to improvement in both liver inflammation and fibrosis.

Intestinal permeability in subjects from two different race groups with diverse stone-risk profiles

It is well established that calcium oxalate stones may be caused by colonic or ileum oxalate (Ox) hyperabsorption (secondary to intestinal dysfunction). Studies have reported that increased intestinal permeability (IP) can cause hyperabsorption of nutrients culminating in passive diffusion of Ox. In South Africa, renal stones occur in the white population (W) but are extremely rare in the black population (B). Previous studies have shown that despite B having a hyperoxalurogenic diet relative to W, urinary Ox in the former is not higher. It has been suggested that different Ox handling mechanisms in the groups are the cause of this disparity. The present study was undertaken to examine whether the IP index, a reliable and accurate measure of intestinal integrity, plays a role in this anomaly. Ten healthy males from each group ingested a dual-sugar isotonic solution containing 5 g lactulose (LA) and 2 g mannitol (MA). IP was assessed by comparing the LA:MA ratio in 5 h urine samples using high performance anion exchange chromatography coupled with pulse amperometric detection to measure the concentration of each sugar. 24 h dietary intake and urine composition were also determined. LA excretion was identical in both groups (0.03 %) while MA excretion was 8.3 % in B and 11.3 % in W. IP index was 0.004 for B and 0.003 for W. It is concluded that IP is not a contributory factor in the apparent different handling of dietary Ox in B and W South Africans. It is speculated that differences in renal transporters may play a role.