Increased intestinal sugar permeability after challenge in children with cow's milk allergy or intolerance

The Role of Gut Microbiota and Leaky Gut in the Pathogenesis of Food Allergy

Food allergy (FA) is a growing public health concern, with an increasing prevalence in Western countries. Increasing evidence suggests that the balance of human gut microbiota and the integrity of our intestinal barrier may play roles in the development of FA. Environmental factors, including industrialization and consumption of highly processed food, can contribute to altering the gut microbiota and the intestinal barrier, increasing the susceptibility to allergic sensitization. Compositional and functional alterations to the gut microbiome have also been associated with FA. In addition, increased permeability of the gut barrier allows the translocation of allergenic molecules, triggering Th2 immune responses. Preclinical and clinical studies have highlighted the potential of probiotics, prebiotics, and postbiotics in the prevention and treatment of FA through enhancing gut barrier function and promoting the restoration of healthy gut microbiota. Finally, fecal microbiota transplantation (FMT) is now being explored as a promising therapeutic strategy to prevent FA in both experimental and clinical studies. In this review article, we aim to explore the complex interplay between intestinal permeability and gut microbiota in the development of FA, as well as depict potential therapeutic strategies.

Dysregulation of intestinal epithelial CFTR-dependent Cl- ion transport and paracellular barrier function drives gastrointestinal symptoms of food-induced anaphylaxis in mice

Food-triggered anaphylaxis can encompass a variety of systemic and intestinal symptoms. Murine-based and clinical studies have revealed a role for histamine and H1R and H2R-pathway in the systemic response; however, the molecular processes that regulate the gastrointestinal (GI) response are not as well defined. In the present study, by utilizing an IgE-mast cell (MC)-dependent experimental model of oral antigen-induced anaphylaxis, we define the intestinal epithelial response during a food-induced anaphylactic reaction. We show that oral allergen-challenge stimulates a rapid dysregulation of intestinal epithelial transcellular and paracellular transport that was associated with the development of secretory diarrhea. Allergen-challenge induced (1) a rapid intestinal epithelial Cftr-dependent Cl- secretory response and (2) paracellular macromolecular leak that was associated with modification in epithelial intercellular junction proteins claudin-1, 2, 3 and 5, E-cadherin and desmosomal cadherins. OVA-induced Cftr-dependent Cl- secretion and junctional protein degradation was rapid occurring and was sustained for 72 h following allergen-challenge. Blockade of both the proteolytic activity and Cl- secretory response was required to alleviate intestinal symptoms of food-induced anaphylaxis. Collectively, these data suggest that the GI symptom of food-induced anaphylactic reaction, secretory diarrhea, is a consequence of CFTR-dependent Cl- secretion and proteolytic activity.

Palatability of hypoallergenic formulas for cow's milk allergy and healthcare professional recommendation

BACKGROUND

Cows 'milk protein allergy (CMPA) is the most common food allergy in infants in the United Kingdom. Infants with CMPA who are not exclusively breastfed require a substitute hypoallergenic formula, which are perceived as having a poor palatability. This study compares the palatability of different extensively hydrolysed formulas (EHFs) and explores healthcare professional (HCP) expectations of how palatability impacts infants and their families.

METHODS

Healthcare professional with experience of CMPA were recruited to take part in a home palatability test of four EHFs [Aptamil Pepti 1, Nutricia Ltd. (EHF W1); Althera, Nestle Health Science (EHF W2); Similac Alimentum, Abbott (EHF C1); Nutramigen LGG 1, Mead Johnson (EHF C2)] using a blind taste procedure. A randomised, complete block design was used to minimise order and carry-over biases. Participants completed a questionnaire about the impact of formula palatability on infants and their families.

RESULTS

A total of 100 HCPs took part (51 dietitians and 49 general practitioners). Overall, whey-based lactose-containing EHFs were ranked the most palatable: EHF W1 by 77% of participants and EHF W2 by 20%. EHF W1 was liked significantly more (P < 0.0001) than the other formulas. The vast majority of participants agreed that better palatability would result in an increased chance of non-rejection (96%), more content families (92%) and decreased healthcare costs (90%).

CONCLUSION

Amongst HCPs who manage infants with CMPA, whey-based lactose-containing EHFs were ranked the most palatable. HCPs expected that good palatability would result in better acceptance, more content infants and families, alongside decreased wastage and healthcare costs.

From clinical uncertainties to precision medicine: the emerging role of the gut barrier and microbiome in small bowel functional diseases

Over the last decade, remarkable progress has been made in the understanding of disease pathophysiology. Many new theories expound on the importance of emerging factors such as microbiome influences, genomics/omics, stem cells, innate intestinal immunity or mucosal barrier complexities. This has introduced a further dimension of uncertainty into clinical decision-making, but equally, may shed some light on less well-understood and difficult to manage conditions. Areas covered: Comprehensive review of the literature on gut barrier and microbiome relevant to small bowel pathology. A PubMed/Medline search from 1990 to April 2017 was undertaken and papers from this range were included. Expert commentary: The scenario of clinical uncertainty is well-illustrated by functional gastrointestinal disorders (FGIDs). The movement towards achieving a better understanding of FGIDs is expressed in the Rome IV guidelines. Novel diagnostic and therapeutic protocols focused on the GB and SB microbiome can facilitate diagnosis, management and improve our understanding of the underlying pathological mechanisms in FGIDs.

Effect of caloric restriction on gut permeability, inflammation markers, and fecal microbiota in obese women

Recent findings suggest an association between obesity, loss of gut barrier function and changes in microbiota profiles. Our primary objective was to examine the effect of caloric restriction and subsequent weight reduction on gut permeability in obese women. The impact on inflammatory markers and fecal microbiota was also investigated. The 4-week very-low calorie diet (VLCD, 800 kcal/day) induced a mean weight loss of 6.9 ± 1.9 kg accompanied by a reduction in HOMA-IR (Homeostasis model assessment-insulin resistance), fasting plasma glucose and insulin, plasma leptin, and leptin gene expression in subcutaneous adipose tissue. Plasma high-molecular weight adiponectin (HMW adiponectin) was significantly increased after VLCD. Plasma levels of high-sensitivity C-reactive protein (hsCRP) and lipopolysaccharide-binding protein (LBP) were significantly decreased after 28 days of VLCD. Using three different methods, gut paracellular permeability was decreased after VLCD. These changes in clinical parameters were not associated with major consistent changes in dominant bacterial communities in feces. In summary, a 4-week caloric restriction resulted in significant weight loss, improved gut barrier integrity and reduced systemic inflammation in obese women.

Food contact materials and gut health: Implications for toxicity assessment and relevance of high molecular weight migrants

Gut health is determined by an intact epithelial barrier and balanced gut microbiota, both involved in the regulation of immune responses in the gut. Disruption of this system contributes to the etiology of various non-communicable diseases, including intestinal, metabolic, and autoimmune disorders. Studies suggest that some direct food additives, but also some food contaminants, such as pesticide residues and substances migrating from food contact materials (FCMs), may adversely affect the gut barrier or gut microbiota. Here, we focus on gut-related effects of FCM-relevant substances (e.g. surfactants, N-ring containing substances, nanoparticles, and antimicrobials) and show that gut health is an underappreciated target in the toxicity assessment of FCMs. Understanding FCMs' impact on gut health requires more attention to ensure safety and prevent gut-related chronic diseases. Our review further points to the existence of large population subgroups with an increased intestinal permeability; this may lead to higher uptake of compounds of not only low (<1000 Da) but also high (>1000 Da) molecular weight. We discuss the potential toxicological relevance of high molecular weight compounds in the gut and suggest that the scientific justification for the application of a molecular weight-based cut-off in risk assessment of FCMs should be reevaluated.

Impact of elimination diets on growth and nutritional status in children with multiple food allergies

BACKGROUND

Impairment of growth has been reported in food-allergic children. It is not known whether this is related to the extent of food allergies. We sought to compare growth, nutritional status, and nutrient intake in children with food allergy either avoiding cow's milk or avoiding cow's milk and wheat, which are staples of the diet in young children.

METHODS

Infants and young children with challenge-proven allergy were recruited to this prospective study. They were strictly avoiding their allergic food triggers, either cow's milk, or cow's milk and wheat. They were counseled by a dietitian specialized in food allergies on food avoidance diets and nutritionally adequate supplementation at regular intervals. A 3-day food diary was kept. Children's height, weight, and laboratory data for nutritional parameters were monitored at 8-month intervals.

RESULTS

A total of 18 patients avoiding milk and 28 patients avoiding milk and wheat were evaluated at an average of 12, 21, and 28 months of age. During the follow-up, the markers of nutritional status, nutrient intake or height for age, and weight for height were comparable between the two groups, although the means for anthropometric measures were below the average for age in both groups.

CONCLUSIONS

The extent of food elimination diet has no impact on growth or nutritional status of food-allergic children, when diet is adequately supplemented. Close physician and dietitian follow-up are essential for food-allergic children when avoiding one or more foods, which are staples of the diet.

Intestinal permeability--a new target for disease prevention and therapy

Data are accumulating that emphasize the important role of the intestinal barrier and intestinal permeability for health and disease. However, these terms are poorly defined, their assessment is a matter of debate, and their clinical significance is not clearly established. In the present review, current knowledge on mucosal barrier and its role in disease prevention and therapy is summarized. First, the relevant terms 'intestinal barrier' and 'intestinal permeability' are defined. Secondly, the key element of the intestinal barrier affecting permeability are described. This barrier represents a huge mucosal surface, where billions of bacteria face the largest immune system of our body. On the one hand, an intact intestinal barrier protects the human organism against invasion of microorganisms and toxins, on the other hand, this barrier must be open to absorb essential fluids and nutrients. Such opposing goals are achieved by a complex anatomical and functional structure the intestinal barrier consists of, the functional status of which is described by 'intestinal permeability'. Third, the regulation of intestinal permeability by diet and bacteria is depicted. In particular, potential barrier disruptors such as hypoperfusion of the gut, infections and toxins, but also selected over-dosed nutrients, drugs, and other lifestyle factors have to be considered. In the fourth part, the means to assess intestinal permeability are presented and critically discussed. The means vary enormously and probably assess different functional components of the barrier. The barrier assessments are further hindered by the natural variability of this functional entity depending on species and genes as well as on diet and other environmental factors. In the final part, we discuss selected diseases associated with increased intestinal permeability such as critically illness, inflammatory bowel diseases, celiac disease, food allergy, irritable bowel syndrome, and--more recently recognized--obesity and metabolic diseases. All these diseases are characterized by inflammation that might be triggered by the translocation of luminal components into the host. In summary, intestinal permeability, which is a feature of intestinal barrier function, is increasingly recognized as being of relevance for health and disease, and therefore, this topic warrants more attention.

Non-celiac gluten sensitivity: literature review

BACKGROUND

A significant percentage of the general population report problems caused by wheat and/or gluten ingestion, even though they do not have celiac disease (CD) or wheat allergy (WA), because they test negative both for CD-specific serology and histopathology and for immunoglobulin E (IgE)-mediated assays. Most patients report both gastrointestinal and nongastrointestinal symptoms, and all report improvement of symptoms on a gluten-free diet. This clinical condition has been named non-celiac gluten sensitivity (NCGS).

AIM

We attempt to define the current pathogenic, clinical, and diagnostic criteria of this "new" disease, to provide a practical view that might be useful to evaluate, diagnose, and manage NCGS patients.

METHODS

We reviewed the international literature through PubMed and Medline, using the search terms "wheat (hyper)sensitivity," "wheat allergy," "wheat intolerance," "gluten (hyper)sensitivity," and "gluten intolerance," and we discuss current knowledge about NCGS.

RESULTS

It has been demonstrated that patients suffering from NCGS are a heterogeneous group, composed of several subgroups, each characterized by different pathogenesis, clinical history, and, probably, clinical course. NCGS diagnosis can be reached only by excluding CD and WA. Recent evidence shows that a personal history of food allergy in infancy, coexistent atopy, positive for immunoglobulin G (IgG) antigliadin antibodies and flow cytometric basophil activation test, with wheat and duodenal and/or ileum-colon intraepithelial and lamina propria eosinophil counts, could be useful to identify NCGS patients.

CONCLUSIONS

Future research should aim to identify reliable biomarkers for NCGS diagnosis and to better define the different NCGS subgroups. Key teaching points: • Most patients report both gastrointestinal and nongastrointestinal symptoms, and all agree that there is an improvement of symptoms on a gluten-free diet. • NCGS diagnosis can be reached only by excluding celiac disease and wheat allergy. • Patients suffering from NCGS are a heterogeneous group, composed of several subgroups, each characterized by different pathogenesis, clinical history, and, probably, clinical course. • A personal history of food allergy in infancy, coexistent atopy, positive IgG antigliadin antibodies (AGA) and flow cytometric basophil activation test, with wheat and duodenal and/or ileum-colon intraepithelial and lamina propria eosinophil counts, could be useful to identify NCGS patients. • Future research should aim to identify reliable biomarkers for NCGS diagnosis and to better define the different NCGS subgroup.

Intestinal permeability in children with food allergy on specific elimination diets

BACKGROUND

Children with food allergy have been shown to have increased small intestinal permeability (IP) following ingestion of the offending food as well as during elimination diets. We investigated IP in asymptomatic food allergic children during an elimination diet to identify clinical characteristics associated with altered IP.

METHODS

Urinary recovery ratios of lactulose and mannitol (L/M) were determined 5 h following ingestion of 7.5 g of lactulose and 2 g of mannitol in 131 cow's milk and egg allergic children. An L/M ratio of ≥0.025 was considered abnormal based upon previously established laboratory internal references. A chart review was conducted to assess the clinical characteristics of these patients.

RESULTS

A total of 50 (38%) of the 131 children (median 6.7, range 4.8-8.9 yr; 66.2% male) with food allergy had elevated IP while asymptomatic on strict elimination diets. Age and height negatively correlated with IP. However, in the regression model analysis, abnormal IP was associated with shorter stature independently of age. Otherwise, food allergic patients with increased IP were comparable in gender, nutritional status, age of onset of food allergy, history of reactions, atopic diseases, and family history of food allergies to those with normal IP.

CONCLUSIONS

Elevated IP was found in about one-third of asymptomatic food allergic children on elimination diets and was associated with shorter stature. Our results suggest that increased IP may be an intrinsic trait in a subset of food allergic children. However, large, prospective studies are necessary to determine the role of impaired intestinal barrier in food allergy.

Food-induced anaphylaxis: mast cells as modulators of anaphylactic severity

A food-induced anaphylactic reaction can occur within seconds to a few hours following exposure to the causal food allergen and often affects multiple organ systems including gastrointestinal, cutaneous, respiratory, and cardiovascular. A conundrum in the allergy field is that consumption of the same allergen can cause reactions of vastly different severity in separate individuals; one patient may experience a mild non-life-threatening reaction characterized by pruritis of lips or urticaria whereas another may experience a life-threatening reaction that involves respiratory and cardiovascular compromise leading to loss of consciousness and sometimes death. While there are tests available to determine the predictive risk value of a positive food challenge test or clinical reactivity, there is currently no reliable method to distinguish between individuals who are at risk of mild non-life-threatening versus life-threatening reaction. Recent research has significantly advanced our understanding of the involvement of immune pathways in the effector phase of food-induced anaphylaxis; a void remains regarding our understanding of the contribution of these pathways to severity of disease. In this review, we discuss mild non-life-threatening versus life-threatening food-induced anaphylaxis and factors (co-morbidities and immune activation) that predispose individuals to more severe disease. Furthermore, we summarize recent advancements in our understanding of the involvement of underlying immune pathways in systemic and food-induced anaphylaxis in mouse systems and discuss how these pathways may contribute to more severe disease phenotype.

Intestinal epithelial barrier dysfunction in food hypersensitivity

Intestinal epithelial barrier plays a critical role in the maintenance of gut homeostasis by limiting the penetration of luminal bacteria and dietary allergens, yet allowing antigen sampling for the generation of tolerance. Undigested proteins normally do not gain access to the lamina propria due to physical exclusion by tight junctions at the cell-cell contact sites and intracellular degradation by lysosomal enzymes in enterocytes. An intriguing question then arises: how do macromolecular food antigens cross the epithelial barrier? This review discusses the epithelial barrier dysfunction in sensitized intestine with special emphasis on the molecular mechanism of the enhanced transcytotic rates of allergens. The sensitization phase of allergy is characterized by antigen-induced cross-linking of IgE bound to high affinity FcεRI on mast cell surface, leading to anaphylactic responses. Recent studies have demonstrated that prior to mast cell activation, food allergens are transported in large quantity across the epithelium and are protected from lysosomal degradation by binding to cell surface IgE and low-affinity receptor CD23/FcεRII. Improved immunotherapies are currently under study including anti-IgE and anti-CD23 antibodies for the management of atopic disorders.

[Food allergy]

Food allergy is a growing health issue; its prevalence has exponentially increased in the past years, and it is situated around 4-5% of the general population. Health professionals will frequently have to deal with the management of affected patients. Only a minor number of foods cause the majority of allergic reactions. In Spain, milk, egg and fish are the most frequent sensitizers in children with food allergy; in adults, fruits and nuts, followed by fish and sea-food are the main food allergens. Clinical manifestations range from mild cutaneous reactions to life-threatening anaphylaxis. Therefore, an accurate diagnosis is crucial, as well as a correct medical treatment of reactions. Furthermore, patients and care-givers should be instructed on allergen avoidance and on the use of emergency kits in case of accidental ingestion.

Combined use of noninvasive tests is useful in the initial diagnostic approach to a child with suspected inflammatory bowel disease

OBJECTIVE

To assess the effectiveness of the combined use of fecal calprotectin (FC), anti-Saccharomyces cerevisiae antibody (ASCA), perinuclear staining antineutrophil antibody (pANCA), small intestinal permeability test (IP), and bowel wall ultrasonography measurement (BWUS) in the diagnostic work-up of children with suspected inflammatory bowel disease (IBD).

METHODS

All children referred for initial assessment of possible IBD were eligible. Patients with symptoms or signs (right-lower quadrant mass, perianal disease, or hematochezia) mandating a complete work-up for IBD were excluded. All enrolled patients underwent a clinical, laboratory, radiographic, and endoscopic evaluation including biopsy examinations. The immunoglobulin (Ig)G and IgA ASCA, IgG pANCA, FC, IP, and BWUS were tested in all patients at the initial assessment.

RESULTS

A final diagnosis of IBD was made in 27 patients: 17 Crohn disease and 10 ulcerative colitis. Eighteen children had other gastrointestinal diagnoses (8 functional bowel disorders, 5 food allergy-mediated diseases, 4 infectious enterocolitis, 1 familial Mediterranean fever). In patients with simultaneous abnormal values of FC, BWUS, and ASCA/pANCA, the estimated probability of having IBD was 99.47%. Patients with negative results on all tests had a 0.69% of probability of IBD.

CONCLUSIONS

The incorporation of noninvasive diagnostic tests into the initial diagnostic approach may avoid unnecessary invasive procedures and facilitate clinical decision-making when the diagnosis of IBD in children is initially uncertain.

Gastrointestinal food allergy: new insights into pathophysiology and clinical perspectives

Adverse reactions to food that result in gastrointestinal symptoms are common in the general population; while only a minority of such individuals will have symptoms due to immunologic reactions to foods, gastrointestinal food allergies do exist in both children and adults. These immune reactions are mediated by immunoglobulin E-dependent and -independent mechanisms involving mast cells, eosinophils, and other immune cells, but the complexity of the underlying mechanisms of pathogenesis have yet to be fully defined. Knowledge of the spectrum of adverse reactions to foods that affect the digestive system, including gastrointestinal food allergy, is essential to correctly diagnose and manage the subset of patients with immunologically mediated adverse reactions to foods. Potentially fatal reactions to food necessitate careful instruction and monitoring on the part of health care workers involved in the care of individuals at risk of anaphylaxis. New methods of diagnosis and novel strategies for treatment, including immunologic modulation and the development of hypoallergenic foods, are exciting developments in the field of food allergy.

Glucagon-like peptide-2-enhanced barrier function reduces pathophysiology in a model of food allergy

Penetration of the gut epithelial barrier by intact luminal antigen is necessary for immunologically mediated pathophysiology in the context of food allergy. We investigated if glucagon-like peptide-2 (GLP-2) could affect immediate hypersensitivity and late-phase allergic inflammation in a murine model. Mice were sensitized to horseradish peroxidase (HRP); studies were conducted 14 days later. Mice were treated with 5 microg GLP-2 subcutaneously 4 h before antigen challenge. For immediate hypersensitivity, jejunal segments in Ussing chambers were challenged by luminal HRP antigen. GLP-2 treatment reduced the uptake of HRP and the antigen-induced secretory response after luminal challenge. GLP-2 appears to reduce macromolecular uptake independent of the CD23-mediated enhanced antigen uptake pathway. For the late phase, mice were gavaged with antigen, and 48 h later the function and histology of the jejunum were examined. GLP-2 prevented the usual prolonged permeability defect and reduced the number of inflammatory cells in the mucosa. Our studies demonstrate that a single treatment of sensitized mice with GLP diminishes both immediate and late-phase hypersensitivity reactions characteristic of food allergy by inhibiting transepithelial uptake of antigen.

Intestinal barrier: an interface between health and disease

The intestine constitutes the largest interface between a person and his or her environment, and an intact intestinal barrier is thus essential in maintaining health and preventing tissue injury and several diseases. The intestinal barrier has various immunological and non-immunological components. The epithelial barrier is one of the most important non-immunological components. Hyperpermeability of this barrier is believed to contribute to the pathogenesis of several gastrointestinal disorders including inflammatory bowel disease, celiac disease and food allergy. Hence, assessing barrier integrity is of the utmost importance. One of the more quantitative gauges for this assessment is transepithelial permeability of various molecular probes, among which sugars are commonly used. Measures of intestinal permeability might also be useful as markers for assessment of prognosis and follow up in various gastrointestinal disorders. The present article is a review of the normal and abnormal functioning of the intestinal barrier, the diseases that can result from loss of barrier integrity, and some promising agents and strategies for restoring barrier normality and integrity.

Altered intestinal permeability to mannitol in diabetes mellitus type I

BACKGROUND

Intestinal permeability has seldom been investigated in diabetes mellitus, even though patients frequently report gastrointestinal symptoms, and it has recently been shown that the prevalence of celiac disease associated with diabetes mellitus is higher than expected.

METHODS

Intestinal permeability to cellobiose and mannitol was investigated in 31 patients affected by type I uncomplicated diabetes mellitus. Values were compared with those obtained in 32 normal subjects.

RESULTS

The percentage of mannitol recovery was far higher than normal in two thirds of the investigated patients and correlated with the length of disease, even though the probes' ratio (cellobiose/mannitol) was in the normal range.

CONCLUSIONS

A not previously reported increase of intestinal permeability to mannitol, clear-cut and not associated with that of the larger probe, is found in type I uncomplicated diabetes mellitus. These results may describe a primary feature of type I diabetes mellitus and the initial steps of evolution to celiac disease.