The effect of poorly absorbed solute on intestinal absorption

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.

Improved Hygroscopicity and Bioavailability of Solid Dispersion of Red Ginseng Extract with Silicon Dioxide

This study aims to develop a powder formulation for the Korean red ginseng extract (RGE) and to evaluate its in vitro and in vivo formulation characteristics. The solid dispersion of RGE was prepared with hydrophilic carriers using a freeze-drying method. After conducting the water sorption–desorption isothermogram (relative humidity between 30 and 70% RH), differential scanning calorimetry thermal behavior, dissolution test, and intestinal permeation study, a solid dispersion formulation of RGE and silicon dioxide (RGE-SiO₂) was selected. RGE-SiO₂ formulation increased intestinal permeability of ginsenoside Rb1 (GRb1), GRb2, GRc, and GRd by 1.6-fold in rat jejunal segments as measured by the Ussing chamber system. A 1.6- to 1.8-fold increase in plasma exposure of GRb1, GRb2, GRc, and GRd in rats was observed following oral administration of RGE-SiO₂ (375 mg/kg as RGE). No significant difference was observed in the time to reach maximum concentration (T_max) and half-life in comparison to those in RGE administered rats (375 mg/kg). In conclusion, formulating solid dispersion of RGE with amorphous SiO₂, the powder formulation of RGE was successfully formulated with improved hygroscopicity, increased intestinal permeability, and enhanced oral bioavailability and is therefore suitable for processing solid formulations of RGE product.

Environmental Impact of the Presence, Distribution, and Use of Artificial Sweeteners as Emerging Sources of Pollution

Artificial sweeteners are posing a new threat to the environment. The water ecosystem is the primary recipient of these emerging contaminants. Once ingested, sufficient amount of these artificial sweeteners escape unchanged from the human body and are added to the environment. However, some are added in the form of their breakdown products through excretion. Artificial sweeteners are resistant to wastewater treatment processes and are therefore continuously introduced into the water environments. However, the environmental behavior, fate, and long-term ecotoxicological contributions of artificial sweeteners in our water resources still remain largely unknown. Some artificial sweeteners like saccharin are used as a food additive in animal feeds. It also forms the degradation product of the sulfonylurea herbicides. All artificial sweeteners enter into the wastewater treatment plants from the industries and households. From the effluents, they finally reside into the receiving environmental bodies including wastewaters, groundwaters, and surface waters. The global production of these sweeteners is several hundred tons annually and is continuously being added into the environment.

Non-nutritive artificial sweeteners as an emerging contaminant in environment: A global review and risks perspectives

Generally, non-nutritive artificial sweeteners are widely utilized as sugar substitute in various applications. With various applications, non-nutritive artificial sweeteners are now being recognized as emerging contaminants with high water persistence and are chemically stable in environment. Although non-nutritive artificial sweeteners were documented on their occurrence in environment, yet their potential impacts to environment and human health remain ambiguous. Therefore, this review was prepared to provide a more comprehensive insight of non-nutritive artificial sweeteners in environment matrixes by highlighting special concerns on human health and environmental risks. Precisely, this review monitors the exploration of non-nutritive artificial sweeteners occurrences as an emerging contaminants in environment worldwide and their associated risks to human as well as environment. At present, there are a total of 24 non-nutritive artificial sweeteners' studies with regards to their occurrence in the environment from 38 locations globally, spanning across Europe including United Kingdoms, Canada, United States and Asia. Overall, the quantitative findings suggested that the occurrence of non-nutritive artificial sweeteners is present in surface water, tap water, groundwater, seawater, lakes and atmosphere. Among these environmental matrixes, surface water was found as the most studied matrix involving non-nutritive artificial sweeteners. However, findings on non-nutritive artificial sweeteners impacts on human health and environment are limited to understanding its overall potential impacts and risks. Additionally, this review also serves as a framework for future monitoring plans and environmental legislative to better control these emerging contaminants in environment.

In Vitro and In Vivo Inhibition of Intestinal Glucose Transport by Guava (Psidium Guajava) Extracts

SCOPE

Known pharmacological activities of guava (Psidium guajava) include modulation of blood glucose levels. However, mechanistic details remain unclear in many cases.

METHODS AND RESULTS

This study investigated the effects of different guava leaf and fruit extracts on intestinal glucose transport in vitro and on postprandial glucose levels in vivo. Substantial dose- and time-dependent glucose transport inhibition (up to 80%) was observed for both guava fruit and leaf extracts, at conceivable physiological concentrations in Caco-2 cells. Using sodium-containing (both glucose transporters, sodium-dependent glucose transporter 1 [SGLT1] and glucose transporter 2 [GLUT2], are active) and sodium-free (only GLUT2 is active) conditions, we show that inhibition of GLUT2 was greater than that of SGLT1. Inhibitory properties of guava extracts also remained stable after digestive juice treatment, indicating a good chemical stability of the active substances. Furthermore, we could unequivocally show that guava extracts significantly reduced blood glucose levels (≈fourfold reduction) in a time-dependent manner in vivo (C57BL/6N mice). Extracts were characterized with respect to their main putative bioactive compounds (polyphenols) using HPLC and LC-MS.

CONCLUSION

The data demonstrated that guava leaf and fruit extracts can potentially contribute to the regulation of blood glucose levels.

Assessment of Environmental Enteric Dysfunction in the SHINE Trial: Methods and Challenges

Environmental enteric dysfunction (EED) is a virtually ubiquitous, but poorly defined, disorder of the small intestine among people living in conditions of poverty, which begins early in infancy and persists. EED is characterized by altered gut structure and function, leading to reduced absorptive surface area and impaired intestinal barrier function. It is hypothesized that recurrent exposure to fecal pathogens and changes in the composition of the intestinal microbiota initiate this process, which leads to a self-perpetuating cycle of pathology. We view EED as a primary gut disorder that drives chronic systemic inflammation, leading to growth hormone resistance and impaired linear growth. There is currently no accepted case definition or gold-standard biomarker of EED, making field studies challenging. The Sanitation Hygiene Infant Nutrition Efficacy (SHINE) trial in Zimbabwe is evaluating the independent and combined effects of a package of infant feeding and/or water, sanitation, and hygiene interventions on stunting and anemia. SHINE therefore provides an opportunity to longitudinally evaluate EED in a well-characterized cohort of infants, using a panel of biomarkers along the hypothesized causal pathway. Our aims are to describe the evolution of EED during infancy, ascertain its contribution to stunting, and investigate the impact of the randomized interventions on the EED pathway. In this article, we describe current concepts of EED, challenges in defining the condition, and our approach to evaluating EED in the SHINE trial.

Use of the lactulose to mannitol ratio to evaluate childhood environmental enteric dysfunction: a systematic review

Childhood gut dysfunction (enteropathy) is common in resource-poor environments. Stunting is its presumed major consequence. Identification of biomarkers of gut dysfunction could identify the presence of, and, ideally, assess interventions for, enteropathy. Classically, enteropathy has been identified histopathologically. However, less invasive assays may be more sensitive for detecting earlier perturbations reflecting specific functional derangements. The most commonly used test has been the urinary lactulose to mannitol ratio (L:M), which primarily assesses gut leakiness, and which also measures absorption. We systematically reviewed the L:M literature published from 2000 to 2010 pertinent to children in developing country settings, and identified 25 relevant publications representing heterogeneous studies. We conclude that the L:M test has many attributes, including reflecting 2 physiologic processes (absorption and permeability) and likely correlation with growth failure consequent to child gut dysfunction. However, improved test technical performance, data reporting, and correlation with host phenotypes are needed to maximize the utility of this test.

The effects of melatonin on colonic transit time in normal controls and IBS patients

OBJECTIVES

The role of melatonin in regulating gut motility in human subjects is not clear. The aim of this study was to investigate the effects of exogenous melatonin on colonic transit time (CTT) in healthy subjects and in patients with irritable bowel syndrome (IBS).

METHODS

Colonic transit time was measured in 17 healthy controls using the radio-opaque, blue dye, and Bristol stool form score method before and after 30 days of melatonin treatment 3 mg daily. A double blind cross-over study aimed at measuring CTT was also performed in 17 matched IBS patients using the blue dye and Bristol stool form score methods. The patients were randomized and received either melatonin 3 mg or placebo daily for 8 weeks, followed by a 4-week washout, and then placebo or melatonin in the reverse order for a second 8-week period.

RESULTS

The melatonin treatment of the control subjects caused an increase in CTT (mean+/-SD) from 27.4+/-10.5 to 37.4+/-23.8 h (P=0.04). Compared with the CTT of the controls (25.2+/-7.7), that of the constipation-predominant IBS patients appeared prolonged-65.2+/-33.3 h (P<0.01). The CTT did not change significantly in IBS patients after melatonin treatment.

CONCLUSION

Melatonin may be a promising candidate for the future research of agents that can modulate bowel motility.

Paracellular nutrient absorption in a gum-feeding new world primate, the common marmoset Callithrix jacchus

The common marmoset is one of the few callitrichid species that is not threatened or endangered in the wild, and is widely used in biomedical research, yet relatively little is understood about its digestive physiology. Dietary specialization on plant exudates has lead to relatively reduced small intestines, yet the common marmoset has exceptional dietary breadth, allowing it to successfully utilize a variety of habitats. We predicted that passive, paracellular nutrient absorption would be used by the common marmoset to a greater extent than in other non-flying mammals. We measured the bioavailability and rates of absorption of two metabolically inert carbohydrates not transported by mediated pathways (L-rhamnose and cellobiose, molecular masses of 164 and 342, respectively) to measure paracellular uptake, and of a non-metabolized D-glucose analog (3-O-methyl-D-glucose) to measure total uptake by both mediated and paracellular pathways. We found high bioavailability of 3-O-methyl-D-glucose (83+/-5%), and much higher bioavailability of the paracellular probes than in similarly sized non-flying mammals (30+/-3% and 19+/-2% for L-rhamnose and cellobiose, respectively). Passive, paracellular nutrient absorption accounts for around 30% of total glucose absorption in common marmosets and intestinal permeability is significantly higher than in humans, the only other species of primate measured to date. This may allow the common marmoset to maintain high digestive efficiency when feeding on higher quality foods (fruit, arthropods, gums with higher proportions of simple sugars), in spite of relatively reduced small intestines correlated with adaptations for fermentative digestion of plant gums. We find no evidence to support, in primates, the hypothesis that reliance on paracellular nutrient absorption should increase with body size in mammals, but suggest instead that it may be associated with small body size and/or taxon-specific adaptations to diet.

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

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

Combined LDI/SAT test to evaluate intestinal lactose digestion and mucosa permeability

BACKGROUND

Intestinal mucosal damage causes impaired digestive capacity and increased mucosal permeability. Quantification of damage can be used to improve treatment options. Currently, the Lactose Digestion Index (LDI) and the Sugar Absorption Test (SAT) are used for evaluation. The investigation studied whether both tests could be combined to provide a useful multifunctional test and whether measurements in blood (LDI) could be replaced by measurements in urine.

MATERIALS AND METHODS

The LDI (25 g 13C-lactose, 0.5 g 2H-glucose), the SAT (5 g lactulose, 1 g L-rhamnose) and the LDI/SAT combination test were performed in seven lactose-digesting and eight lactose-maldigesting adults. Plasma glucose 13C-enrichment was determined by gas-chromatography/combustion/isotope ratio mass-spectrometry (GC/C/IRMS), 2H enrichment determined by gas-chromatography/mass-spectrometry (GC/MS) and urinary sugars by gas-chromatography (GC).

RESULTS

The results of the separate LDI test were not different from those of the LDI/SAT in the lactose-digester group (0.82 +/- 0.06 vs. 0.81 +/- 0.09), nor in the lactose-maldigester group (0.36 +/- 0.12 vs. 0.35 +/- 0.06). A significant correlation was found between the 10-h urinary-lactose/lactulose ratio and the LDI (R2 = 0.71, P < 0.01). There were no differences in the lactulose/L-rhamnose ratio between lactose-digesters and lactose-maldigesters using both the SAT and LDI/SAT tests.

CONCLUSION

The LDI/SAT test is a reliable method of measuring digestion and permeability simultaneously. The 10-h period urinary lactose/lactulose excretion ratio following lactose consumption reflects lactose digestive capacity.

Melatonin improves bowel symptoms in female patients with irritable bowel syndrome: a double-blind placebo-controlled study

BACKGROUND

Melatonin is involved in the regulation of gastrointestinal motility and sensation.

AIM

To determine the potential therapeutic effects of melatonin in irritable bowel syndrome (IBS).

METHOD

Seventeen female patients satisfying the Rome II criteria for IBS were randomized to receive either melatonin 3 mg nocte or identically appearing placebo 1 nocte for 8 weeks, followed by a 4-week washout period and placebo or melatonin in the reverse order for another 8 weeks. Three validated questionnaires - the GI symptom, the sleep questionnaires and the Hospital Anxiety and Depression Scale - were used to assess symptom severity and to compute the IBS, sleep and anxiety/depression scores, respectively.

RESULTS

Improvements in mean IBS scores were significantly greater after treatment with melatonin (3.9 +/- 2.6) than with placebo (1.3 +/- 4.0, P = 0.037). Percent response rate, defined as percentage of subjects achieving mild-to-excellent improvement in IBS symptoms, was also greater in the melatonin-treated arm (88% vs. 47%, P = 0.04). The changes in mean sleep, anxiety, and depression scores were similar with either melatonin or placebo treatment.

CONCLUSIONS

Melatonin is a promising therapeutic agent for IBS. Its therapeutic effect is independent of its effects on sleep, anxiety or depression.

Evaluation of a triple sugar test of colonic permeability in humans

AIM

Conventional dual sugar tests of intestinal permeability assess only the stomach and small intestine. A novel triple sugar method of assessing colonic permeability has recently been described in animals. This utilizes the non-fermented sweetener sucralose, in addition to conventional sugars. It has been postulated that this test enables the simultaneous assessment of small-intestinal and colonic barrier function in humans. The aim of this study was to evaluate the triple sugar test using healthy volunteers and ileostomists.

METHODS

Twenty-one healthy volunteers and 18 ileostomists underwent the triple sugar test. After an overnight fast, subjects drank a solution containing lactulose (5 g), rhamnose (1 g) and sucralose (5 g). Urine was collected for 0-5 h and 5-19 h. Urinary sugars were quantified using HPLC, and 5 and 24-h excretion calculated. Nineteen control subjects and 16 ileostomists also underwent a 51Cr-EDTA permeability test. Permeability data were presented as medians (IQR), and differences between groups analysed with Mann-Whitney U-tests.

RESULTS

Lactulose excretion and the 5-h lactulose/rhamnose (L/R) ratio were similar in controls and ileostomists [L/R ratio 0.024 (0.022-0.034) vs. 0.025 (0.022-0.035), P = 0.955]. Twenty-four hours excretion of sucralose was significantly higher in control subjects compared with ileostomists [1.41% (1.17-1.68) vs. 0.96% (0.64-1.2), P = 0.003]. The same pattern was seen with 51Cr-EDTA [2.73% (2.06-3.76) vs. 2.06% (1.55-2.71), P = 0.037] and with lactulose [0.52% (0.42-0.60) vs. 0.25% (0.16-0.35), P = 0.002].

CONCLUSIONS

Both sucralose and 51Cr-EDTA underwent significant colonic absorption. A significant amount of lactulose also appeared to be absorbed in the colon. This unexpected finding requires further study.

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.

In vivo measurement of intestinal absorption using 3-0 methylglucose in short bowel syndrome

PURPOSE

The management of patients with short bowel syndrome is complicated by the paucity of methods to assess in vivo the absorptive capacity of the remaining bowel. The purpose of this experiment was to assess the feasibility of using urinary recovery of 3-0 methylglucose (3-0 MG) as a quantitative measure of carbohydrate absorptive capacity, comparing it with in vivo absorption and in vitro glucose transport studies.

METHODS

Male Sprague Dawley rats underwent either a 90% proximal small bowel resection or sham resection (n = 8 in each group). Animals were pair fed, weighed, and followed up for 14 days. A 3-day balance study was done, measuring feed intake and fecal output for percentages of fat and energy absorption. Animals were gavaged with 3-0 MG/Mannitol solution, and 4-hour urinary recovery of sugars was assessed using high-performance liquid chromatography (HPLC). On different days these studies were repeated with increasing amounts of added normal glucose (1 mol/L, 1.25 mol/L, and 1.5 mol/L) in the gavage solution given to compete for 3-0 MG transport, and thus increase the "sensitivity" of the test. Animals were then killed, and sections of intestine taken for in vitro assessment of glucose transport using radiolabeled 3-0 MG in Ussing chambers.

RESULTS

Total energy, carbohydrate, and fat absorption all were reduced significantly in the resected animals, as was 3-0 MG urinary recovery (62.9 +/- 10.5%) in controls versus (35.8 +/- 17.5%) in resected animals (P <.05). 3-0 MG urinary recovery correlated well with dietary carbohydrate absorption (r = 0.74), and with Ussing chamber measures of glucose flux (r = 0.97). Adding exogenous glucose to the test solution to "compete" for 3-0 MG transport sites did not improve sensitivity.

CONCLUSIONS

These results show that 3-0 MG is useful in measuring nutrient absorption capacity in rats after massive small bowel resection. Further studies to validate these methods in human patients with short bowel syndrome are suggested.

Dual sugar permeability testing in diarrheal disease

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSIONS

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

The sensitivity of the lactulose/rhamnose gut permeability test

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Lactose maldigestion in breast-feeding Gambian infants

BACKGROUND

The ability of breast-feeding infants to utilize lactose, the major carbohydrate in breast-milk, is dependent on the presence of the enzyme lactase (E.C.3.2.1.108). Lactase is located in the brush border of the small intestine and because of its exposed position it is extremely vulnerable to pathogenic damage. Breast-fed Gambian infants have poor growth associated with intestinal damage beyond 3-4 months. The aim of this study was to assess the ability of Gambian infants aged 2-15 months (N = 113) to digest lactose and to see how this varied with age, intestinal permeability, and growth performance.

METHODS

Lactose maldigestion was estimated by monthly measurements of urinary lactose and lactulose following an oral dose of the latter.

RESULTS

Both urinary lactose excretion and lactulose maldigestion increased with age (p < 0.0001 ANOVA). Up to 6 months the mean urinary lactose: lactulose excretion ratio was within the quoted normal range (< 0.4). Beyond this age, mean values were hypolactasic. Lactose maldigestion was related to poor growth in both weight and length (r = -0.04, p < 0.0001, after age correction). Although a major part of this relationship was a reflection of the previously reported correlation between intestinal permeability and growth, more than 30% of the association was in addition to the permeability effect. Possible explanations are discussed.

CONCLUSIONS

Moderate-to-severe hypolactasia does occur in breast-fed Gambian infants and is related to poorer-than-expected growth. However, this does not mean that breast milk intake should be reduced as the nutritional and immunological benefits of breast milk continue to outweigh any disadvantages.

Evaluation of differential disaccharide excretion in urine for non-invasive investigation of altered intestinal disaccharidase activity caused by alpha-glucosidase inhibition, primary hypolactasia, and coeliac disease

BACKGROUND/AIM

The reliability of a quantitative method for the non-invasive assessment of intestinal disaccharide hydrolysis was assessed.

METHODS

Differential excretion of intact disaccharide, expressed as ratios of lactulose to appropriate hydrolysable disaccharides in urine collected following combined ingestion, has been investigated in healthy volunteers with drug induced alpha-glucosidase inhibition, in subjects with primary hypolactasia, and patients with coeliac disease.

RESULTS

Oral administration of the alpha-glucosidase inhibitor 'Acarbose' (BAY g 5421, 200 mg) together with sucrose and lactulose increased the urinary sucrose/lactulose excretion ratios (% dose/10 h) fivefold. The effect was quantitatively reproducible, a higher dose of 'Acarbose' (500 mg) increasing the excretion ratio to about 1.0 indicating complete inhibition of intestinal sucrase activity. The suitability of the method for measuring differences in dose/response and duration of action was assessed by comparing three different alpha-glucosidase inhibitors (BAY g 5421, BAY m 1099, and BAY o 1248) and found to be satisfactory. Subjects with primary adult hypolactasia had urine lactose/lactulose excretion ratios raised to values indicating reduced rather than complete absence of lactase activity whereas sucrose/lactulose ratios were not significantly affected. 'Whole' intestinal disaccharidase activity assessed by this method demonstrated impairment of lactase, sucrase, and isomaltase in eight, one, and seven, respectively, of 20 patients with coeliac disease. By contrast in vitro assay of jejunal biopsy tissue indicated pan-disaccharidase deficiency in all but five of these patients. This shows the importance of distinguishing between 'local' and 'whole' intestinal performance.

CONCLUSIONS

Differential urinary excretion of ingested disaccharides provides a reliable, quantitative, and non-invasive technique for assessing profiles of intestinal disaccharidase activity.

Gastrointestinal permeability and absorptive capacity in sepsis

OBJECTIVE

To assess gastrointestinal permeability and functional absorptive capacity in patients with sepsis.

DESIGN

Case control study to analyze gastrointestinal permeability and functional absorptive capacity of septic patients by differential saccharide absorption (from an oral test solution) and excretion.

SETTING

The intensive Therapy Unit of St. Thomas' Hospital, London, UK.

PATIENTS

Twenty patients with a mean Acute Physiology and Chronic Health Evaluation (APACHE) II score of 18.4 who were admitted to the intensive care unit with a diagnosis of sepsis. All patients were on enteral feeding. Patients with abdominal pathology were excluded.

INTERVENTIONS

An oral test solution containing 5 g of lactulose, 1 g of L-rhamnose, 0.5 g of D-xylose, and 0.2 g of 3-O-methyl-D-glucose dissolved in water to a final volume of 100 mL was administered to patients and controls. Urine was collected for 5 hrs starting immediately after administration of the test solution and the saccharide content of the urine was estimated and expressed as a percentage recovery of the oral test solution.

MEASUREMENTS AND MAIN RESULTS

Septic patients had increased lactulose/L-rhamnose urine excretion ratios (0.23 +/- 0.19) compared with control subjects (0.03 +/- 0.01, p < .001), consistent with increased gastrointestinal permeability in sepsis. Septic patients had decreased L-rhamnose/3-O-methyl-D-glucose urine excretion ratios (0.14 +/- 0.07) compared with normal controls (0.28 +/- 0.08, p < .001), consistent with decreased gastrointestinal functional absorptive capacity in sepsis.

CONCLUSIONS

Patients with acute sepsis exhibit increased gastrointestinal permeability and decreased gastrointestinal functional absorptive capacity in comparison with healthy control subjects. These abnormalities may contribute to the pathophysiology of sepsis.

Relationship between small-intestinal transit rate and intestinal absorption of (14)C-labelled mannitol and (51)Cr-labelled ethylenediaminetetraacetic acid in healthy subjects

BACKGROUND

Although the small-intestinal transit rate is generally considered to influence the urinary excretion of markers of intestinal permeability, no study has until now formally addressed the importance of this influence in humans.

METHODS

Ten healthy subjects ingested a test solution containing (99m)Tc-labelled diethylenetriaminepentaacetic acid ((99)mTc-DTPA), (14)C-labelled mannitol ((14)C-mannitol), and (51)Cr-labelled ethylenediaminetetraacetic acid ((51)Cr-EDTA). After ingestion, the small-intestinal transit rate of (99)mTc-DTPA was measured with the gamma camera technique. Urine was collected for time periods of 0-2 h, 2-4 h, and 4-6 h to measure the excretion of absorbed (14)C-mannitol and (51)Cr-EDTA. Moreover, the distribution volume and plasma clearance of (14)C-mannitol and (51)Cr-EDTA were determined in each subject.

RESULTS

A positive correlation was found between mean small-intestinal transit time and 0- to 6-h urinary excretion of (14)C-mannitol. The study did not show any correlation between small-intestinal transit rate and 0- to 6-h urinary excretion of (51)Cr-EDTA. Urinary excretion of neither (14)C-mannitol nor (51)Cr-EDTA was affected by distribution volume or urine volume. A positive correlation was observed between plasma clearance and 0- to 6-h urinary excretion of (14)C-mannitol, whereas plasma clearance did not influence the urinary excretion of (51)Cr-EDTA.

CONCLUSIONS

Small-intestinal transit rate seems to have a significant effect on 0- to 6-h urinary excretion of (14)C-mannitol, whereas small intestinal transit rate does not influence the timed urinary excretion of (51)Cr-EDTA.

Intestinal absorptive capacity, intestinal permeability and jejunal histology in HIV and their relation to diarrhoea

Intestinal function is poorly defined in patients with HIV infection. Absorptive capacity and intestinal permeability were assessed using 3-O-methyl-D-glucose, D-xylose, L-rhamnose, and lactulose in 88 HIV infected patients and the findings were correlated with the degree of immunosuppression (CD4 counts), diarrhoea, wasting, intestinal pathogen status, and histomorphometric analysis of jejunal biopsy samples. Malabsorption of 3-O-methyl-D-glucose and D-xylose was prevalent in all groups of patients with AIDS but not in asymptomatic, well patients with HIV. Malabsorption correlated significantly (r = 0.34-0.56, p < 0.005) with the degree of immune suppression and with body mass index. Increased intestinal permeability was found in all subgroups of patients. The changes in absorption-permeability were of comparable severity to those found in patients with untreated coeliac disease. Jejunal histology, however, showed only mild changes in the villus height/crypt depth ratio as compared with subtotal villus atrophy in coeliac disease. Malabsorption and increased intestinal permeability are common in AIDS patients. Malabsorption, which has nutritional implications, relates more to immune suppression than jejunal morphological changes.

Echo-planar magnetic resonance imaging to assess water volume in the distal small bowel

PURPOSE

Assessment of fluid volumes and flow through the small intestine has in the past only been possible by means of invasive intubation studies on human volunteers. Intubation very likely disturbs gut motility and stimulates secretion.

METHODS

The aim of this study was to utilise the new technique of echo-planar magnetic resonance imaging in order to non-invasively visualise the changing volume of water in the small intestinal lumen. 200 mls of test solution was ingested and water volume assessed using a multi-slice scanning technique on 3 separate days. The solutions were pure water, pure water plus 2.264 or 10 g of mannitol. These were taken on separate days by 8 healthy male volunteers. Regions of interest were constructed in the area of the lower pelvis excluding retroperitoneal structure.

RESULTS

The water content of the lower small intestine did not change significantly over the 4 hours after the control solution. By contrast after both mannitol solutions there was an increase in the amount of water in the distal intestine as assessed by the area under the curve of the volume time profile (Control 51 ml.h (SD +/- 47); mannitol 2.264 g/200 ml 72 ml.h (SD +/- 57); 10 g/200 ml mannitol 115 ml.h (SD +/- 56)). Page's L Trend test showed that the trend for the volume to increase with increasing mannitol concentration to be statistically significant at the 1% level (L = 108).

CONCLUSIONS

The study highlights the potential of echo-planar magnetic resonance imaging to visualise changes in gastrointestinal physiology in a noninvasive manner.

The effect of different concentrations of mannitol in solution on small intestinal transit: implications for drug absorption

The aim of the present study was to investigate the effect that different concentrations of mannitol have on small intestinal transit, and whether any observed effect was concentration dependent. Eight, healthy male subjects each received 200ml of radiolabelled purified water, or a 200ml solution of mannitol at three different concentrations; 0.755g/200ml, 1.509g/200ml and 2.264g/200ml, in a randomised, four way cross-over study. Transit of the radiolabelled solutions was followed by gamma scintigraphy. The study demonstrated no significant differences between the gastric emptying times of the four solutions. Rapid gastric emptying was observed in most cases. The mean small intestinal transit times for the 0.755g/200ml, 1.509g/200ml and 2.264g/200ml mannitol solutions was reduced by 11%, 23% and 34% respectively, when compared to the control solution. The intestinal transit data of the four solutions demonstrate that mannitol has a concentration dependent effect on small intestinal transit. Small concentrations of mannitol included in a pharmaceutical formulation could therefore lead to reduced uptake with any drug exclusively absorbed from the small intestine.

Intestinal disaccharidase activity in human immunodeficiency virus disease

BACKGROUND

The relationship between disaccharidase activity, progression of human immunodeficiency virus (HIV) disease, and diarrhoea and weight loss was investigated.

METHODS

Forty-six HIV-positive patients ingested a solution of lactose, palatinose, sucrose, and lactulose after 24 h of dietary exclusion and overnight fasting, after which urine was collected for 10 h. Urinary disaccharide (activity) ratios-lactose/lactulose (L/LL), palatinose/lactulose (P/LL), and sucrose/lactulose (S/LL)-were measured by thin-layer chromatography.

RESULTS

There was a significant decrease in disaccharidase activity (L/LL, P/LL, and S/LL) with advancing clinical stage of HIV disease (p < 0.05, Wilcoxon rank sum test) as well as decreasing CD4 count (p < 0.05, Spearman correlation). Patients with weight loss/diarrhoea also had significantly (p < 0.05) decreased disaccharidase activity compared with control but not as compared with AIDS patients. Anti-retroviral therapy did not influence disaccharidase activity.

CONCLUSION

Impairment of disaccharidase activity occurs with advancing HIV disease, but its role in HIV patients with weight loss and diarrhoea remains to be determined.

Increased intestinal marker absorption due to regional permeability changes and decreased intestinal transit during sepsis in the rat

BACKGROUND

The intestinal barrier properties are impaired during inflammation and sepsis, but the mechanisms behind this are unknown and were therefore investigated during experimental sepsis in rats.

METHODS

The different-sized intestinal absorption markers 51Cr-labeled ethylenediaminetetraacetic acid (EDTA) and ovalbumin were gavaged to rats made septic by intra-abdominal bacterial implantation and to sham-operated rats. Regional tissue permeability was measured in diffusion chambers, and intestinal transit was evaluated by intestinal accumulation of gavaged 51Cr-EDTA.

RESULTS

In comparison with the sham-operated rats, septic rats had higher 51Cr-EDTA levels in blood and urine and showed a prolonged intestinal transit. Septic rats also had a lower tissue permeability to both markers in the small intestines but higher permeability to ovalbumin in the colon. Rats receiving morphine to decrease intestinal motility showed similar changes, with a decreased intestinal transit and increased marker absorption.

CONCLUSIONS

The results suggest that the increased intestinal absorption during sepsis was due to regional permeability changes and prolonged intestinal transit.

The effect of ingested lactulose on absorption of L-rhamnose, D-xylose, and 3-O-methyl-D-glucose in subjects with ileostomies

BACKGROUND

We have previously shown that small oral doses of poorly absorbed solute can significantly reduce absorption of test sugars in normal volunteers. To confirm these results and investigate the underlying mechanism, the effects of lactulose on absorption of three test sugars in subjects with ileostomies were studied.

METHODS

Ten fasted subjects with ileostomies ingested an isosmolar test solution containing 2.5 g 3-O-methyl-D-glucose, 5.0 g D-xylose, 1.0 g L-rhamnose, and 50 microCi 51Cr-labelled ethylenediaminetetraacetic acid together with a blue dye transit marker. Urine was collected for time periods of 0-5 h and 5-24 h, to measure excretion of absorbed sugars, and ileostomy effluent was saved from 0-5 h and from 5 h until blue dye transit marker was no longer present, to measure small-bowel output of unabsorbed sugars. After 1 week the test was repeated, including 5 g lactulose in the test solution.

RESULTS

Inclusion of lactulose in the test solution significantly reduced the 5 h and 24 h urine excretion of L-rhamnose and D-xylose but not that of 3-O-methyl-D-glucose and increased 0- to 5-h and total ileostomy output of L-rhamnose and D-xylose but not of 3-O-methyl-D-glucose. The presence of lactulose also reduced the time for first appearance of the blue dye transit marker in the effluent and increased effluent volume together with output of electrolyte.

CONCLUSION

Poorly absorbed solute reduces intestinal absorption by retention of fluid and electrolyte, with subsequent intraluminal dilution and acceleration of transit.

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

BACKGROUND

Controversy surrounds the issue of intestinal permeability in patients with coeliac disease, polyethylene glycol 400 indicating reduced and di-/mono-saccharide urine excretion ratios and 51Cr-labeled ethylenediaminetetraacetic acid (EDTA) indicating increased permeability.

METHODS

We assessed the suitability of polyethylene glycol 400, L-rhamnose, lactulose, and 51Cr-EDTA as markers of intestinal permeability by assessing urine excretions after simultaneous intravenous instillation of these markers and after oral administration in normals and patients with coeliac disease.

RESULTS

After intravenous administration the 24-h urine excretion of polyethylene glycol 400, L-rhamnose, lactulose, and 51Cr-EDTA was 40%, 72%, 93%, and 97%, respectively. There was no significant difference between controls and patients with coeliac disease. Oral administration of the markers in an iso- and hyper-osmolar test solution demonstrates reduced permeation due to an osmotic retention effect of lactulose. In contrast, hyperosmolar glycerol increases permeation of all markers except L-rhamnose. Timing of urines and altering osmolarity is important for the behavior of individual markers but does not enhance the discrimination between controls and patients when the differential urine excretion of lactulose/L-rhamnose is used. The sensitivity of the urine excretion ratio of lactulose/L-rhamnose was comparable to that of 51Cr-EDTA used by itself. Whereas lactulose/L-rhamnose and 51Cr-EDTA showed increased intestinal permeability in coeliac disease, the permeation of polyethylene glycol was reduced. Permeation of the markers did not correlate significantly with jejunal histology.

CONCLUSIONS

Correlations of marker permeation rates with test dose osmolarity in controls and patients with coeliac disease shows a variable lack of conformity, suggesting that the markers may permeate the intestine by different routes, which are affected to a different extent in coeliac disease.

A novel HPLC method for the simultaneous quantification of monosaccharides and disaccharides used in tests of intestinal function and permeability

The quantification of monosaccharides and disaccharides used as probes in intestinal function and permeability tests can be technically demanding, detracting from the value of this approach to the indirect assessment of intestinal damage. In this study, a procedure is described for the simultaneous quantification of rhamnose, lactulose, 3-O-methyl-D-glucose and xylose in urine by HPLC using an anion exchange column with pulsed amperometric detection. This method is relatively fast and simple to perform, requiring no pre-treatment of urine samples or post-column derivatization. Accuracy and precision of determinations are illustrated by analytical recoveries (mean percentage +/- S.D., CV., n = 30) for multiple batch analyses of a diluted urine sample containing 20 mg/l of rhamnose (100 +/- 6.8, 6.2%), lactulose (100 +/- 6.1, 5.5%), 3-O-methyl-D-glucose (98 +/- 5.9, 5.5%) and xylose (104 +/- 7.1, 6.5%). Linearity of standard curves indicated that the lower limit for accurate quantification was 0.1 mg/l for all four sugars. Urinary recoveries following oral administration of these sugars to control dogs were determined as a baseline for the investigation of intestinal damage in this species and comparison of chromatograms illustrated enhanced permeability in dogs with gluten-sensitive enteropathy.

Intestinal water and solute absorption studies: comparison of in situ perfusion with chronic isolated loops in rats

The effects of lumenal glucose on jejunal water transport and the influence of glucose-induced water absorption on solute uptake from single-pass perfusions are compared in anesthetized rats in situ and isolated chronic loops in unanesthetized rats in vivo. While the magnitudes of solute membrane permeabilities are consistently higher in the chronic loop system, the effects on water transport and its promotion of jejunal solute uptake are comparable between the two experimental systems. The effect of glucose-induced water absorption on the enhanced/baseline jejunal uptake ratio of the hydrophilic drug, acetaminophen, is greater than that for the lipophilic drug, phenytoin, in both experimental systems. The fact that chronic loop effective solute permeabilities were equivalent to solute membrane permeabilities in situ is consistent with greater lumenal fluid mixing in vivo. In addition, in situ body temperature affects the uptake of phenytoin but not acetaminophen, water, or glucose. This suggests that active and paracellular solute transport is not compromised in situ, while membrane partitioning and diffusion of lipophilic species are more sensitive to experimental conditions.