Dual sugar permeability testing in diarrheal disease

Transcutaneous vagal nerve stimulation protects against stress-induced intestinal barrier dysfunction in healthy adults

BACKGROUND

Intestinal barrier dysfunction is the likely initiating event in multiple human diseases. Currently, there are limited therapeutic strategies to address its dysfunction. Animal studies suggest that vagal nerve stimulation may improve intestinal barrier function, but this has not been evaluated in humans. This study aimed to determine the effect of vagal nerve stimulation on intestinal permeability in adults administered a bolus dose of intravenous corticotropin releasing hormone (CRH) which has been shown to increase small intestinal permeability in healthy human subjects.

METHODS

In a cross-over study, 16 volunteers (median age 34 years, 11 female) were randomized to receive auricular transcutaneous vagal nerve or sham stimulation (10 minutes each side) after intravenous administration of 100 µg of CRH. Intestinal barrier function was measured before and 2 h after each intervention with dual-sugar urine testing (lactulose:mannitol ratio) and intestinal fatty-acid binding protein (I-FABP).

KEY RESULTS

Exposure to CRH increased I-FABP concentrations by a median of 49 (IQR 4-71)% (p = 0.009). Lactulose:mannitol ratios were 0.029 (0.025-0.050) following vagal stimulation compared with 0.062 (0.032-0.170) following sham stimulation (p = 0.0092), representing a fall of 53 (22-71)%. I-FABP concentrations did not change (p = 0.90).

CONCLUSIONS

Brief non-invasive vagal nerve stimulation consistently reduces paracellular permeability of the small intestine after CRH administration, but does not entirely mitigate I-FABP release from the epithelium. Studies of vagal nerve stimulation in disease states are warranted.

Characterization of Upper Gastrointestinal Motility in Infants With Persistent Distress and Non-IgE-mediated Cow's Milk Protein Allergy

BACKGROUND

Persistent crying in infancy is common and may be associated with gastroesophageal reflux disease (GERD) and/or non-IgE-mediated cow's milk protein allergy (CMPA). We aimed to document upper gastrointestinal motility events in infants with CMPA and compare these to findings in infants with functional GERD.

METHODS

Infants aged 2 to 26 weeks with persistent crying, GERD symptoms and possible CMPA were included. Symptoms were recorded by 48-hour cry-fuss chart and validated reflux questionnaire (infant GERD questionnaire [IGERDQ]). Infants underwent a blinded milk elimination-challenge sequence to diagnose CMPA. GERD parameters and mucosal integrity were assessed by 24-hour pH-impedance monitoring before and after cow's milk protein (CMP) elimination. C-octanoate breath testing for gastric emptying dynamics, dual-sugar intestinal permeability, fecal calprotectin, and serum vitamin D were also measured.

RESULTS

Fifty infants (mean age 13 ± 7 weeks; 27 boys) were enrolled. On the basis of CMP elimination-challenge outcomes, 14 (28%) were categorized as non-IgE-mediated CMPA, and 17 (34%) were not allergic to milk; 12 infants with equivocal findings, and 7 with incomplete data were excluded. There were no baseline differences in GERD parameters between infants with and without CMPA. In the CMPA group, CMP elimination resulted in a significant reduction in reflux symptoms, esophageal acid exposure (reflux index), acid clearance time, and an increase in esophageal mucosal impedance.

CONCLUSIONS

In infants with persistent crying, upper gastrointestinal motility parameters did not reliably differentiate between non-IgE-mediated CMPA and functional GERD. In the group with non-IgE-mediated CMPA, elimination of CMP significantly improved GERD symptoms, esophageal peristaltic function, and mucosal integrity.

Gut microbiome dysbiosis and increased intestinal permeability in children with islet autoimmunity and type 1 diabetes: A prospective cohort study

AIMS/HYPOTHESIS

To investigate the longitudinal relationship between the gut microbiome, circulating short chain fatty acids (SCFAs) and intestinal permeability in children with islet autoimmunity or type 1 diabetes and controls.

METHODS

We analyzed the gut bacterial microbiome, plasma SCFAs, small intestinal permeability and dietary intake in 47 children with islet autoimmunity or recent-onset type 1 diabetes and in 41 unrelated or sibling controls over a median (range) of 13 (2-34) months follow-up.

RESULTS

Children with multiple islet autoantibodies (≥2 IA) or type 1 diabetes had gut microbiome dysbiosis. Anti-inflammatory Prevotella and Butyricimonas genera were less abundant and these changes were not explained by differences in diet. Small intestinal permeability measured by blood lactulose:rhamnose ratio was higher in type 1 diabetes. Children with ≥2 IA who progressed to type 1 diabetes (progressors), compared to those who did not progress, had higher intestinal permeability (mean [SE] difference +5.14 [2.0], 95% confidence interval [CI] 1.21, 9.07, P = .006), lower within-sample (alpha) microbial diversity (31.3 [11.2], 95% CI 9.3, 53.3, P = .005), and lower abundance of SCFA-producing bacteria. Alpha diversity (observed richness) correlated with plasma acetate levels in all groups combined (regression coefficient [SE] 0.57 [0.21], 95% CI 0.15, 0.99 P = .008).

CONCLUSIONS/INTERPRETATION

Children with ≥2 IA who progress to diabetes, like those with recent-onset diabetes, have gut microbiome dysbiosis associated with increased intestinal permeability. Interventions that expand gut microbial diversity, in particular SCFA-producing bacteria, may have a role to decrease progression to diabetes in children at-risk.

Intestinal Barrier Maturation in Very Low Birthweight Infants: Relationship to Feeding and Antibiotic Exposure

OBJECTIVE

To test the hypothesis that feeding and antibiotic exposures affect intestinal barrier maturation in preterm infants, we serially measured intestinal permeability (IP) biomarkers in infants <33 weeks gestation (gestational age [GA]) during the first 2 weeks of life.

STUDY DESIGN

Eligible infants <33 weeks GA were enrolled within 4 days of birth in a prospective study of IP biomarkers (NCT01756040). Study participants received the nonmetabolized sugars lactulose/rhamnose enterally on study days 1, 8, and 15 and lactulose/rhamnose were measured in urine by high-performance liquid chromatography. Serum zonulin and fecal alpha-1-anti-trypsin, 2 other IP markers, were measured by semiquantitative Western blot and ELISA, respectively.

RESULTS

In a cohort of 43 subjects, the lactulose/rhamnose ratio was increased on day 1 and decreased over 2 weeks, but remained higher in infants born at ≤28 weeks of gestation compared with IP in infants born at >28 weeks of gestation. Exclusive breastmilk feeding was associated with more rapid maturation in intestinal barrier function. A cluster analysis of 35 subjects who had urine samples from all time points revealed 3 IP patterns (cluster 1, normal maturation: n = 20 [57%]); cluster 2, decreased IP during the first week and subsequent substantial increase: n = 5 [14%]); and cluster 3, delayed maturation: n = 10 [29%]). There were trends toward more prolonged antibiotic exposure (P = .092) and delayed initiation of feeding ≥4 days (P = .064) in infants with abnormal IP patterns.

CONCLUSIONS

Intestinal barrier maturation in preterm infants is GA and postnatal age dependent, and is influenced by feeding with a maturational effect of breastmilk feeding and possibly by antibiotic exposures.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01756040.

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.

Zinc-fortified oral rehydration solution improved intestinal permeability and small intestinal mucosal recovery

A randomized double-blind placebo-controlled study was conducted in children admitted to hospital with gastroenteritis (≥3 loose stools per day). All were treated for 5 days following admission with either zinc (Zn, 3 mg) or without Zn-fortified rice-based oral rehydration solution (ORS). (13)C-sucrose breath test (SBT) and intestinal permeability (lactulose/rhamnose or L/R ratio) were performed concurrently prior to commencement of ORS with or without Zn and at day 5 post-admission. There was a significant improvement in the SBT results in both the Zn-fortified group, median (5th-95th percentile) 2.1% (0.4% to 8.3%) versus 4.4% (0.4% to 10.4%), P < .05, and control group, 1.4% (0.1% to 5.4%) versus 4.3% (0.4% to 11.4%), P < .05, between the day of admission and day 5 post-admission. In the Zn-fortified group, there was also a significant improvement in L/R ratio between the day of admission and day 5 post-admission, 53.0 (19.5-90.6) versus 17.7 (13.4-83.2), P < .05. Low levels of Zn improved intestinal permeability but did not enhance short-term recovery following diarrheal illness.

Efficacy of Lactobacillus GG in aboriginal children with acute diarrhoeal disease: a randomised clinical trial

OBJECTIVE

The effectiveness of probiotic therapy for acute rotavirus infectious diarrhoea in an indigenous setting with bacterial/parasitic diarrhoea is unclear. In the present study, we assessed the efficacy of probiotics in Australian Aboriginal children in the Northern Territory admitted to hospital with diarrhoeal disease.

PATIENTS AND METHODS

A randomised double-blind placebo-controlled study was conducted in Aboriginal children (ages 4 months-2 years), admitted to hospital with acute diarrhoeal disease (>3 loose stools per day). Children received either oral Lactobacillus GG (5 x 10(9) colony-forming units 3 times per day for 3 days; n = 33) or placebo (n = 31). Small intestinal functional capacity was assessed by the noninvasive 13C-sucrose breath test on days 1 and 4.

RESULTS

Both groups showed mean improvement in the sucrose breath test after 4 days; however, there was no difference (mean, 95% confidence interval) between probiotic (2.9 [cumulative percentage of dose recovered at 90 minutes]; 1.7-4.2) and placebo (3.7; 2.3-5.2) groups. Probiotics did not change the duration of diarrhoea, total diarrhoea stools, or diarrhoea score compared with placebo. There was a significant (P < 0.05) difference in diarrhoea frequency on day 2 between probiotics (3.3 [loose stools]; 2.5-4.3) and placebo (4.7; 3.8-5.7) groups.

CONCLUSIONS

Lactobacillus GG did not appear to enhance short-term recovery following acute diarrhoeal illness in this setting.

13C-sucrose breath test: novel use of a noninvasive biomarker of environmental gut health

OBJECTIVE

Environmental enteropathy syndrome may compromise growth and predispose to infectious diseases in children in the developing world, including Australian Aboriginal children from remote communities of the Northern Territory. In this study, we described the use of a biomarker (13)C-sucrose breath test (SBT) to measure enterocyte sucrase activity as a marker of small intestinal villus integrity and function.

METHODS

This was a hospital-based prospective case-control study of Aboriginal and non-Aboriginal children with and without acute diarrheal disease. Using the SBT, we compared 36 Aboriginal case subjects admitted to a hospital (18 diarrheal and 18 nondiarrheal disease), with 7 healthy non-Aboriginal control subjects. Intestinal permeability using the lactulose/rhamnose (L/R) ratio on a timed 90-minute blood test was performed simultaneously with the SBT. The SBT results are expressed as a cumulative percentage of the dose recovered at 90 minutes.

RESULTS

Aboriginal children with acute diarrheal disease have a significantly decreased absorptive capacity, as determined by the SBT, with a mean of 1.9% compared with either Aboriginal children without diarrhea (4.1%) or non-Aboriginal (6.1%) control subjects. The mean L/R ratio in the diarrhea group was 31.8 compared with 11.4 in Aboriginal children without diarrhea. There was a significant inverse correlation between the SBT and the L/R ratio.

CONCLUSIONS

The SBT was able to discriminate among Aboriginal children with diarrhea, asymptomatic Aboriginal children with an underlying environmental enteropathy, and healthy non-Aboriginal controls. This test provides a noninvasive, easy-to-use, integrated marker of the absorptive capacity and integrity of the small intestine and could be a valuable tool in evaluating the efficacy of interventions aimed at improving gut health.

Dual sugar gut-permeability testing on blood drop in animal models

BACKGROUND

Intestinal permeability is determined by measuring nonmetabolized sugars. In animals, intestinal permeability is determined in urine, using cumbersome and expensive metabolic cages. We developed an HPLC method for determining concentrations of lactulose (L) and L-rhamnose (R) in blood-drop of rabbits and mice, and we compared these results with the procedure based on sugars excreted in urine. We measured the intestinal permeability induced by a fragment (DeltaG) of the zonula occludens toxin which opens the paracellular pathway.

METHODS

The animals received sugar solution and later received the same solution+DeltaG. Five-hour urine collection and timed blood tests were performed after ingestion of sugars. Sugars were measured with HPLC, and the percentage of recovered sugars was expressed as L/R ratio.

RESULTS

At 60 min after administration of sugars, the mean L/R ratio for rabbits and mice was 0.026 and 0.052, respectively. At 60 min after administration of sugars+DeltaG, the mean L/R ratio for rabbits and mice was 0.22 and 0.53. The mean L/R ratio in the urine was 0.023 at basal condition and 0.25 after DeltaG ingestion.

CONCLUSIONS

Testing small serum samples for sugar permeability is effective for monitoring changes in permeability of the gut in animals. This cheap simple method allows us to measure in vivo the biological activity of other molecules which modulate the paracellular pathway.

Increased nitric oxide production in acute diarrhoea is associated with abnormal gut permeability, hypokalaemia and malnutrition in tropical Australian aboriginal children

Australian Aboriginal children hospitalized with diarrhoeal disease have severe manifestations with acidosis, hypokalaemia, osmotic diarrhoea and abnormal small bowel permeability. Nitric oxide (NO) production is increased in diarrhoeal disease, but its relationship to mucosal function and diarrhoeal complications is not known. We examined the relationship between NO production and complications of acute diarrhoea in Aboriginal and non-Aboriginal children between February 1998 and February 2000. We enrolled 318 children admitted to Royal Darwin Hospital into one of three groups: acute diarrhoea, non-diarrhoeal controls with no inflammatory illness, and non-diarrhoeal controls with inflammatory illness. Nitric oxide production was measured by urine nitrate-creatinine (NOx/Cr) excretion on a low nitrate diet. Small bowel intestinal permeability was measured by the lactulose-rhamnose (L/R) ratio on a timed blood specimen. The NOx/Cr ratios were markedly elevated in Aboriginal diarrhoeal cases (geometric mean [GM] = 1.23, 95% confidence interval [95% CI] 1.07-1.44), lowest in non-Aboriginal non-inflammatory controls (GM = 0.13, 95% CI 0.10-0.16) and intermediate in all other groups (GM = 0.35, 95% CI 0.28-0.43). Convalescent levels (day 5) in the Aboriginal diarrhoeal group (GM = 1.02, 95% CI 0.82-1.28) were slower to fall than L/R ratios. Multivariate analysis in the diarrhoeal group indicated that high NO production was associated with abnormal permeability, hypokalaemia and malnutrition, but not with the severity of diarrhoea, acidosis or osmotic diarrhoea. We concluded that increased NO production may contribute to impaired mucosal barrier function and hypokalaemia in acute gastroenteritis, which may be the cost of the known gut-protective and antimicrobial effects mediated by NO in acute intestinal inflammation.

Milk formulas in acute gastroenteritis and malnutrition: a randomized trial

OBJECTIVE

To compare three low-lactose milk formulas differing in osmolality and degree of protein hydrolysis in the treatment of diarrhoea and malnutrition in subjects with high rates of lactose intolerance, osmotic diarrhoea and a tropical/environmental enteropathy.

METHODS

A randomized double-blind trial of 180 Aboriginal children under 3 years of age admitted with acute diarrhoea and/or malnutrition was carried out. The intervention milk formulas were: (i) De-Lact, a low-osmolality lactose-free formula; (ii) O-Lac, a lactose-free formula; and (iii) Alfaré, a partially hydrolysed formula. Outcome measures were diarrhoeal severity, weight gain, formula palatability and changes in intestinal permeability (L/R ratios).

RESULTS

The duration of diarrhoea in days (mean; 95% confidence interval) was significantly longer on Alfaré (8.5; 7.0-10.0) compared to De-Lact (6.1; 5.0-7.2) and O-Lac (6.9; 5.6-8.1; P = 0.04). There were no differences in mean intake between formulas, but palatability of Alfaré was significantly worse (P < 0.01) than the other formulas. Over the trial 5 days, improvement in L/R ratios was significantly greater (P = 0.05) for De-Lact (18.6; 10.6-26.6) than for Alfaré (8.5; 2.1-14.9). Weight gain was not significantly different between the three formulas, except in a malnourished subgroup who had better weight gain on De-Lact (P = 0.05).

CONCLUSIONS

In these Aboriginal children with diarrhoea and growth failure, a low osmolality milk was associated with better outcomes and a partially hydrolysed formula with less improvement in mucosal recovery, suggesting that cow's milk protein intolerance is not contributing to greater diarrhoeal severity or enteropathy in Aboriginal children.

Enteric pathogens, intestinal permeability and nitric oxide production in acute gastroenteritis

BACKGROUND

Aboriginal children hospitalized with diarrheal disease in northern Australia have high rates of acidosis, hypokalemia and osmotic diarrhea, as well as abnormal small bowel permeability and elevated nitric oxide (NO) production.

METHODS

In a study of 291 diarrheal admissions and 84 controls, we examined the relationship of diarrheal severity outcomes with specific enteric pathogens. NO production was measured by urine nitrate plus nitrite excretion on a low nitrate diet, small bowel permeability by the lactulose:rhamnose ratio on a timed blood specimen and stool pathogens by standard microbiologic investigations and PCR.

RESULTS

The addition of diagnostic tests for diarrheagenic Escherichia coli to standard stool microbiologic testing increased the rate of specific diagnoses from 53% to 75%, but with multiple pathogens isolated from 34%. The most frequently isolated pathogens from diarrheal patients were enteroaggregative E. coli (28.9%), rotavirus (26.5%), enteropathogenic E. coli (17.2%), Salmonella spp. (10.7%), Cryptosporidium parvum (7.2%) and Strongyloides stercoralis (7.2%). High geometric mean permeability ratios (95% confidence intervals) occurred with rotavirus (19.6; 15.3 to 25.1), enteroaggregative E. coli (21.2; 15.3 to 29.3) and Cryptosporidium (23.0; 15.1 to 35.1) compared with 9.4 (6.8 to 13.1) for no pathogens. NO production was highest for Cryptosporidium (3.7; 2.3 to 6.1) compared with 0.6 (0.4 to 1.1) for no pathogens. Multiple regression analysis revealed significant associations (P < 0.001) for rotavirus with acidosis and osmotic diarrhea, for Strongyloides with wasting and hypokalemia and for Cryptospoidium with severe and prolonged diarrhea.

CONCLUSIONS

Cryptosporidium, Strongyloides, rotavirus and enteroaggregative E. coli are important contributors to the severe manifestations of acute gastroenteritis in Australian Aboriginal children.

Small bowel intestinal permeability in Australian aboriginal children

OBJECTIVE

To show that the severity of diarrheal disease in Aboriginal children in tropical Australia is a consequence of underlying small intestinal mucosal damage.

STUDY DESIGN

A prospective study of 338 Aboriginal admissions compared to 37 non-Aboriginal children, both diarrhea cases and controls. Intestinal permeability was measured by lactulose-rhamnose (L/R) ratios on a timed 90-minute blood test.

RESULTS

For diarrheal admissions, significantly more Aboriginal (vs. non-Aboriginal children) had hypokalemia (70 vs. 10%), acidosis (65 vs. 29%), moderate to severe dehydration (52 vs. 19%) and a longer mean length of stay (mean 8.9 vs. 3.9 days). Mean L/R ratios (95% confidence intervals) in Aboriginal children (diarrhea vs. controls) were 16.5 (14.6-18.7) vs. 4.5 (3.8-5.3) compared to 7.7 (4.4-13.3) vs. 2.5 (1.8-3.4), respectively, in non-Aboriginals. Abnormal permeability ratios (> 5.6) consistent with tropical-environmental enteropathy syndrome were found in 36% (27/75) of Aboriginal controls compared to none of the non-Aboriginal controls. On multiple regression, the factors associated with high L/R ratios were diarrheal severity ( < 0.001), acidosis ( = 0.007) and hypokalemia ( = 0.04).

CONCLUSIONS

An underlying tropical-environmental enteropathy contributes to the severity of acute gastroenteritis in Aboriginal children. Diarrheal complications, such as acidosis, hypokalemia, and osmotic diarrhea are associated with high L/R ratios, reflecting greater small intestinal mucosal damage.

Childhood infections in the tropical north of Australia

In the tropical north of Australia there are high rates of infections in Aboriginal children living in remote communities. In addition to the burden of respiratory infections, diarrhoeal disease and skin sepsis, there are high rates of acute rheumatic fever, outbreaks of poststreptococcal glomerulonephritis and gonococcal conjunctivitis, endemic trachoma and various intestinal parasites. A number of infections generally restricted to the tropics are also present and can cause disease in both indigenous and non-indigenous children. These include melioidosis, Murray Valley encephalitis and dengue on the east coast. With global warming, these infections may become more common and more widespread within Australia and the potential for establishment of introduced infections such as Japanese encephalitis and malaria may increase.