Small intestinal permeability in normal Sudanese subjects: evidence of tropical enteropathy

Undernutrition, Vitamin A and Iron Deficiency Are Associated with Impaired Intestinal Mucosal Permeability in Young Bangladeshi Children Assessed by Lactulose/Mannitol Test

BACKGROUND

Lactulose/mannitol (L:M) test has been used as a non-invasive marker of intestinal mucosal -integrity and -permeability (enteropathy). We investigated the association of enteropathy with anthropometrics, micronutrient- status, and morbidity in children.

METHODS

The urine and blood samples were collected from 925 children aged 6-24 months residing in Mirpur slum of Dhaka, Bangladesh during November 2009 to April 2013. L:M test and micronutrient status were assessed in the laboratory of International Centre for Diarrhoeal Diseases Research, Bangladesh (icddr,b) following standard procedure.

RESULTS

Mean±SD age of the children was 13.2±5.2 months and 47.8% were female. Urinary- lactulose recovery was 0.264±0.236, mannitol recovery was 3.423±3.952, and L:M was 0.109±0.158. An overall negative correlation (Spearman's-rho) of L:M was found with age (rs = -0.087; p = 0.004), weight-for-age (rs = -0.077; p = 0.010), weight-for-length (rs = -0.060; p = 0.034), mid-upper-arm-circumference (rs = -0.098; p = 0.001) and plasma-retinol (rs = -0.105; p = 0.002); and a positive correlation with plasma α-1-acid glycoprotein (rs = 0.066; p = 0.027). However, most of the correlations were not very strong. Approximately 44% of children had enteropathy as reflected by L:M of ≥0.09. Logistic regression analysis revealed that younger age (infancy) (adjusted odds ratio (AOR) = 1.35; p = 0.027), diarrhea (AOR = 4.00; p = 0.039) or fever (AOR = 2.18; p = 0.003) within previous three days of L:M test were the risk factors of enteropathy (L:M of ≥0.09).

CONCLUSIONS

Enteropathy (high L:M) is associated with younger age, undernutrition, low vitamin A and iron status, and infection particularly diarrhea and fever.

Environmental enteric dysfunction: pathogenesis, diagnosis, and clinical consequences

Stunting is common in young children in developing countries, and is associated with increased morbidity, developmental delays, and mortality. Its complex pathogenesis likely involves poor intrauterine and postnatal nutrition, exposure to microbes, and the metabolic consequences of repeated infections. Acquired enteropathy affecting both gut structure and function likely plays a significant role in this outcome, especially in the first few months of life, and serve as a precursor to later interactions of infection and malnutrition. However, the lack of validated clinical diagnostic criteria has limited the ability to study its role, identify causative factors, and determine cost-effective interventions. This review addresses these issues through a historical approach, and provides recommendations to define and validate a working clinical diagnosis and to guide critical research in this area to effectively proceed. Prevention of early gut functional changes and inflammation may preclude or mitigate the later adverse vicious cycle of malnutrition and infection.

Diagnosing small bowel malabsorption: a review

Malabsorption encompasses dysfunctions occurring during the digestion and absorption of nutrients. A small proportion of patients presents with chronic diarrhoea. A clinical history supportive of malabsorption may guide investigations toward either the small bowel or pancreas. Serological testing for coeliac disease will determine most cases without invasive investigations. In the clinical context of persisting weight loss and malnutrition, small bowel enteropathy may be investigated with small intestinal biopsies. Small bowel absorptive capacity and permeability might be measured by oral sugar-mix ingestion. Further, approaches to the investigation of malabsorption might also involve the detection in faeces of a substance that has not been absorbed. A variation of the latter is the use of breath testing which relies on the breakdown of the malabsorbed test substance by colonic flora. Measurement of protein absorption is difficult and unreliable; it is, therefore, rarely advocated in clinical settings. No single biological marker confirming a diagnosis of small bowel malabsorption or small bowel integrity is presently available in clinical practice. Plasma citrulline concentration, an amino acid not incorporated into endogenous or exogenous proteins, has been extensively used in research studies and supportive results are establishing its concentration as a reliable quantitative biomarker of enterocyte absorptive capacity.

Implications of acquired environmental enteric dysfunction for growth and stunting in infants and children living in low- and middle-income countries

Changes in small bowel function early in infancy in developing countries are increasingly being demonstrated, probably accompanied by altered mucosal architecture in most individuals, including reduced enterocyte mass and evidence of immune activation and inflammation in the mucosa. These alterations appear to be the result of factors of uncertain nature in the environment, and may be a cause of growth faltering and stunting in young children. For these reasons, this constellation of findings is being referred to as environmental enteropathy, or as we propose herein, environmental enteric dysfunction. If the causes were known and effective interventions were available, strategies and policies to intervene at--or possibly before--birth could be developed and promoted in order to prevent subsequent malnutrition and recurrent infection, which are known to interact in a cyclical and synergistic manner in a downward clinical course often ending in death. Resources would be mobilized and applied differently, and the emphasis would change from treatment to prevention. In order to move in this highly desired direction, investments in research will be required to establish the criteria to assess environmental enteric dysfunction, determine its predictive value for growth faltering and stunting, identify the causes, and propose and test potential interventions. The concepts and tools are available. What is required is the decision to move forward along this pathway to better health for infants and children in low-income countries.

Intestinal mucosal permeability of children with cefaclor-associated serum sickness-like reactions

Although the serum sickness-like reaction (SSLR) in children after the administration of cefaclor has long been recognized, the exact mechanism of cefaclor-associated SSLR remains unclear. This study aims to investigate the association between intestinal mucosal permeability and cefaclor-associated SSLR in children. A total of 82 pediatric patients with upper respiratory tract infection following the cefaclor therapy was divided into cefaclor-associated SSLR positive group and negative group based on the presence or absence of SSLR after taking cefaclor, and 30 healthy volunteers served as control group. Urinary lactulose/mannitol (L/M) ratios and serum diamine oxidase (DAO) levels were determined in all cases on days 7, 9, 11, 13, and 15 after oral administration of cefaclor. The children in the control group were given the same measurements after enrollment in this study. From days 7 to 13, the urinary L/M ratio of children with cefaclor SSLR gradually increased and reached to the highest level of 0.38 ± 0.14 on day 13. Compared with the cefaclor-associated SSLR negative group and control group, urinary L/M ratios increased significantly in the cefaclor SSLR positive group on days 7, 9, 11, 13, and 15 after taking cefaclor, and serum levels of DAO following the treatment of cefaclor increased significantly in children with cefaclor SSLR on days 9, 11, 13, and 15. No significant difference in urinary L/M ratios and serum levels of DAO between SSLR negative group and control group through the entire experiment was observed. In conclusion, administration of cefaclor may induce SSLR in children by increasing the intestinal mucosal permeability and/or affecting the integrity of the intestinal mucosa. Determinations of urinary L/M ratios and serum DAO levels may be helpful for observing or predicting the occurrence of SSLR after administration of cefaclor, which will encourage physicians to proceed with extreme caution when prescribing cefaclor for pediatric patients.

Intestinal mucosal permeability of severely underweight and nonmalnourished Bangladeshi children and effects of nutritional rehabilitation

OBJECTIVE

Lactulose/mannitol (L/M) intestinal permeability tests were completed to compare the intestinal function of severely underweight children recovering from diarrhea and other illnesses and of nonmalnourished children from the same communities, and to evaluate the effects of food supplementation, with or without psychosocial stimulation, on the changes in intestinal function among the underweight children.

PATIENTS AND METHODS

Seventy-seven malnourished children completed intestinal permeability studies at baseline and 3 months after receiving 1 of the following randomly assigned treatment regimens: group-C--fortnightly follow-up at community-based follow-up units, including growth monitoring and promotion, health education, and micronutrient supplementation, n = 17; group-SF--same as group-C plus supplementary food (SF) to provide 150 to 300 kcal/day, n = 23; group-PS--same as group-C plus psychosocial stimulation (PS), n = 17; or group-SF + PS--same as group-C plus SF and PS, n = 20. Seventeen nonmalnourished children were included as comparison subjects.

RESULTS

The malnourished children's mean ± SD initial age was 13.1 ± 4.0 months, their mean weight-for-age z score was -3.82 ± 0.61, and their median (interquartile range) urinary L/M recovery ratio was 0.16 (0.10-0.28). Eighty-four percent of the children had L/M ≥ 0.07, suggestive of impaired intestinal function. The median L/M of the malnourished children was significantly greater than that of 17 relatively well-nourished children (median 0.09; interquartile range 0.05-0.12; P = 0.001). There were no significant differences in baseline characteristics of the severely malnourished children by treatment group. Following treatment, the L/M ratio improved in all of the groups (P < 0.001), but there were no significant differences in these changes by treatment group. There was a significant positive association between weight gain and the magnitude of improvement in L/M ratio (r = 0.30, P = 0.012).

CONCLUSIONS

Intestinal mucosal function, as measured by sugar permeability, is impaired among severely underweight children. Intestinal permeability improves in relation to weight gain, but intestinal mucosal recovery is not specifically related to the types or amount of food supplementation or PS provided in this trial.

Tropical enteropathy: a T-cell-mediated crypt hyperplastic enteropathy

OBJECTIVE

Tropical enteropathy is widespread throughout the tropics, but its pathogenesis is unknown. T-cell activation has been demonstrated to result in enteropathy in vitro and in animal models, and occurs in untreated patients with coeliac disease. We have therefore examined the hypothesis that T-cell activation is important in the pathogenesis of tropical enteropathy.

PATIENTS AND METHODS

Healthy black Zambian subjects were compared with black and white South Africans. Quantitative microscopy was conducted on distal duodenal biopsies. Mucosal T-cell activation was quantitated by dual colour immunofluorescence staining for CD3 plus CD69 or HLA-DR. Crypt proliferation was measured by direct counting of Feulgen-stained mitotic figures, and systemic immune activation by assay of serum tumour necrosis factor alpha (TNF-alpha).

RESULTS

Villous height was reduced (P = 0.0004), crypt depth increased (P < 0.0001), and mitoses per crypt increased (P = 0.014) in black Zambians compared with black and white South Africans. Mucosal thickness was similar. Intraepithelial lymphocyte count was increased in the black groups compared with whites (P = 0.03). CD3+CD69+ (P = 0.0007) and CD3+HLA-DR+ (P < 0.0001) expression was increased in black Zambians compared with black and white South Africans. Serum TNF-alpha was similar in all groups.

CONCLUSIONS

Tropical enteropathy is associated with mucosal T-cell activation and crypt hyperplasia. Tropical enteropathy occurs in the absence of malnutrition, diarrhoea or systemic illness.

Intestinal permeability in strongyloidiasis

The objective of the present study was to assess intestinal permeability in patients with infection caused by Strongyloides stercoralis. Twenty-six patients (16 women and 10 men), mean age 45.9, with a diagnosis of strongyloidiasis were evaluated. For comparison, 25 healthy volunteers (18 women and 7 men), mean age 44.9, without digestive disorders or intestinal parasites served as normal controls. Intestinal permeability was measured on the basis of urinary radioactivity levels during the 24 h following oral administration of chromium-labeled ethylenediaminetetraacetic acid ((51)Cr-EDTA) expressed as percentage of the ingested dose. The urinary excretion of (51)Cr-EDTA was significantly reduced in patients with strongyloidiasis compared to controls (1.60 +/- 0.74 and 3.10 +/- 1.40, respectively, P = 0.0001). Intestinal permeability is diminished in strongyloidiasis. Abnormalities in mucus secretion and intestinal motility and loss of macromolecules could explain the impaired intestinal permeability.

Epidemiology of altered intestinal permeability to lactulose and mannitol in Guatemalan infants

BACKGROUND

Subclinical alterations of small intestinal function have been reported frequently in tropical countries. Studies of small intestinal permeability to lactulose and mannitol were therefore completed in Guatemalan infants from a low-income, periurban community to assess the prevalence of altered intestinal function and the factors associated with this condition.

METHODS

Two hundred studies were successfully completed in 158 infants who had been free of diarrhea for at least 1 week before the day of study. Urinary concentrations of lactulose and mannitol during the 5-hour period after ingestion of 400 mg/kg body weight of lactulose and 100 mg/kg body weight of mannitol were measured by gas-liquid chromatography and compared by age group, feeding practices, anthropometric indexes, and serum iron and zinc concentrations.

RESULTS

The overall prevalence of altered intestinal permeability (defined as a ratio of urinary recovery of lactulose to mannitol [L/M] > or =0.07) was 30%. The urinary L/M recovery ratio was positively associated with age; low weight for age; and, in infants less than 6 months of age, non-breast-feeding. Children with serum iron concentrations less than 7.16 microM/l (40 [microg/dl) had higher median L/M ratios (L/M = 0.068; 95% confidence interval [CI], 0.054, 0.085) than those with iron levels higher than this cutoff (L/M = 0.052; CI = 0.046, 0.058; p = 0.038). The median urinary L/M recovery ratio in 10 currently asymptomatic infants who had diarrhea during the week before testing (0.087; CI = 0.49, 0.154) was higher than that in children who had been free from diarrhea for at least 1 week (0.052; CI = 0.048, 0.056; p = 0.01).

CONCLUSION

Age, feeding practices, low weight-for-age, low serum iron concentration, and recent diarrhea were all associated with altered intestinal function in this group of Guatemalan infants.

Beriberi in a well-nourished Amazonian population

Beriberi is an endemic disease among the Naporuna indigenous people of Ecuadorean Amazonia (annual morbidity rate of 1.5%). A total of 47 patients with dry beriberi were seen at the Franklin Tello Hospital, Napo, during 1995-1996; a similar incidence was observed in previous years. No wet beriberi was found. Although the diagnosis of the disease was made clinically, an effective and quick response to thiamine treatment excluded other differential diagnoses, such as tropical ataxic neuropathy. Although indigenous people have several possible dietetic risk factors, none of them adequately explain the disease's high incidence. Some suggestions are made for the high incidence of beriberi among this Amazonian people but its cause remains unknown.

Tropical sprue and subclinical enteropathy: a vision for the nineties

Aside from infectious intestinal diseases with known etiology, there is a group of gastrointestinal disorders mainly affecting the small intestine of individuals predominantly living in and less often visiting or returning from the Third World, usually the tropics, and ranging from asymptomatic structural and/or functional abnormalities of the gastrointestinal mucosa (subclinical enteropathy, SE) to a fully symptomatic condition highlighted by malabsorption of nutrients with associated nutritional deficiencies responsive to folate and broad spectrum antibiotic treatment (tropical sprue, TS). Mounting evidence supports an infectious cause in many instances. The exact nature of the infection, whether initiated and/or perpetuated by enterotoxigenic coliform bacteria, virus(es) or a combination of these, is not clear. Further studies, including those using molecular techniques, are needed in order to clarify various aspects of these widely prevalent disorders.

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.

Intestinal permeability: an overview

The noninvasive assessment of intestinal permeability in humans has a 20-year history. Because the tests are increasingly used in clinical practice and research and because there is much controversy, we reviewed the literature and outlined the potential and possible shortcomings of these procedures. Data was obtained from personal files and from a systemic search through MEDLINE and EMBASE. The principle of the differential urinary excretion of orally administered test markers is explained with reference to the desired physicochemical properties of the markers and how the principle can be exploited to allow assessment of various other gastrointestinal functions. The use of intestinal permeability tests for diagnostic screen for small bowel disease and assessment of responses to treatment, the pathogenesis of disease, normal intestinal physiology, and the effect of drugs and toxins on the intestine is described and reviewed. The controversy surrounding the anatomic location of the permeation pathways that the markers use is highlighted. Noninvasive tests of intestinal permeability have fulfilled early promises of usefulness in clinical practice and research. There is now a need for integrated research into the basic mechanisms of regulatory control of the intestinal barrier function.

The BT-PABA/PAS test in tropical diabetes

A 'screening' test is needed to identify patients with chronic pancreatitis among diabetics in tropical field surveys. We have examined the potential diagnostic yield of the BT-PABA/PAS test of exocrine pancreatic function in this setting. The recoveries of both PABA and PAS in eight healthy controls from Madras, south India, were lower than in controls from Manchester, north west England (mean +/- S.D., 51 +/- 11 vs. 79 +/- 7%, P < 0.001 for PABA; 52 +/- 11% vs. 81 +/- 7%, P < 0.001 for PAS) but the % PABA/PAS excretion index (PEI) was similar (0.96 +/- 0.14 vs. 0.96 +/- 0.06). Using a cut-off value of 0.75 for the PEI in a study group including eight patients with chronic pancreatitis and 26 with primary forms of diabetes, test sensitivity was 75%, specificity 92%, positive predictive value 75%, negative predictive value 92% and efficiency 88%.

Small bowel morphology in British Indian and Afro-Caribbean subjects: evidence of tropical enteropathy

Distal duodenal biopsy specimens taken from 30 white, 35 Indian, and 20 Afro-Caribbean residents of West Birmingham during routine endoscopy for dyspepsia, were assessed by dissecting microscopy and morphometry. Finger-shaped villi were significantly less frequent in the Indian and Afro-Caribbean subjects than in the white subjects when assessed by dissecting microscopy (p less than 0.005), and both immigrant groups had decreased mucosal thickness (p less than 0.01), villous height (p less than 0.001), villous:crypt ratios (p less than 0.01) and enterocyte height (p less than 0.05) compared with the white group. In the Indian subjects, villous height and villous:crypt ratios correlated significantly with the time since the last visit to the Indian subcontinent (p less than 0.005). Serum alkaline phosphatase values were significantly higher in the Indian subjects compared with the whites (p less than 0.02), and serum globulins were increased in both the Afro-Caribbean and Indian subjects (p less than 0.01). There were no correlations between morphometric indices and body habitus or biochemical or haematological indices and the long term effect of the morphological changes is not clear.

Relationship between intestinal permeability to [51Cr]EDTA and inflammatory activity in asymptomatic patients with Crohn's disease

The relationship between intestinal permeability to an oral dose (100 mu Ci) of [51CR]EDTA and the inflammatory activity of Crohn's disease was studied in 63 adult patients (32 unresected and 31 resected) who underwent 162 evaluations. The results of the [51CR]EDTA test were compared with the serum levels of the acute-phase reactant proteins (APRP) and with the result of the [111In]leukocyte scanning, respectively, as an indirect and direct method to assess intestinal inflammation. In a group of healthy adult controls, the upper normal value for the 24-hr urinary [51CR]EDTA excretion was 3.61 (97.5% percentile) and the mean coefficient of variation was 21%. Sensitivity and specificity of the [51CR]EDTA test in identifying active inflammation expressed by increased serum levels of APRP were, respectively, 97% and 54% in the unresected group and 68% and 52% in the resected group of patients. The low specificity of the test was due to the presence of increased [51CR]EDTA urinary excretion in about half the cases with normal serum levels of APRP. The [111In]leukocyte scanning was performed in a subgroup of 11 patients (three unresected and eight resected) with normal serum levels of APRP, six with increased and five with normal [51CR]EDTA urinary excretion. All six patients with increased intestinal permeability had a positive 111In image of mild to moderate degree of activity. A positive 111In scan was present in two of the five patients with normal permeability; these were two resected patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma albumin concentrations and intestinal permeability in Bangladeshi children infected with Ascaris lumbricoides

Plasma albumin concentration and intestinal permeability have been investigated in Bangladeshi children before and 9-14 d after successful treatment for ascariasis. Children infected with A. lumbricoides had lower plasma albumin concentrations than counterparts not harbouring this worm and values increased with successful treatment. Intestinal permeability tests indicated that the children had impaired gastrointestinal function and some loss of mucosal integrity; these factors had not improved 9-14 d after A. lumbricoides expulsion. The lowered nitrogen nutritional status implied by the reduced plasma albumin values in infected children, and the improvement following treatment, are in keeping with previous reports that A. lumbricoides impairs protein digestion or absorption. This may be the basis of the better growth rates of dewormed children in this area.

The pathogenesis and consequence of non steroidal anti-inflammatory drug induced small intestinal inflammation in man

Non steroidal anti-inflammatory drugs (NSAID's) have recently been shown to cause small intestinal inflammation in the majority of patients receiving these on a regular basis for more than one year. The development of inflammation is preceded by an NSAID effect to increase small intestinal permeability. Increased intestinal permeability is shown to be related to drug potency to inhibit cyclooxygenase and the effect is systemically mediated rather than a local irritant one. More recently, increased intestinal permeability due to NSAID's has been reduced by concomitant prostaglandin administration, showing that prostaglandins are essential for maintaining intestinal integrity in man. It is proposed that altered intestinal permeability allows the mucosa to be exposed to bacterial degradation products or other toxins and together with reduced chemotaxic response and altered neutrophil function due to NSAID's, this series of events leads to bacterial invasion of the mucosa which is evident by the techniques of 111Indium leucocyte scans and faecal collections. The consequence of such inflammation is that it may explain intestinal perforations and strictures which are occasionally seen in subjects on NSAID's. Most patients with NSAID-induced small intestinal inflammation may be bleeding from the intestine, loosing protein and some have ileal dysfunction. The small intestine may be a greater source of morbidity than the stomach, in patients receiving NSAID's.