Increased beta-lactoglobulin absorption during rotavirus enteritis in infants: relationship to sugar permeability

The heterogeneous pathogenesis of type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) results from the destruction of pancreatic β-cells that is mediated by the immune system. Multiple genetic and environmental factors found in variable combinations in individual patients are involved in the development of T1DM. Genetic risk is defined by the presence of particular allele combinations, which in the major susceptibility locus (the HLA region) affect T cell recognition and tolerance to foreign and autologous molecules. Multiple other loci also regulate and affect features of specific immune responses and modify the vulnerability of β-cells to inflammatory mediators. Compared with the genetic factors, environmental factors that affect the development of T1DM are less well characterized but contact with particular microorganisms is emerging as an important factor. Certain infections might affect immune regulation, and the role of commensal microorganisms, such as the gut microbiota, are important in the education of the developing immune system. Some evidence also suggests that nutritional factors are important. Multiple islet-specific autoantibodies are found in the circulation from a few weeks to up to 20 years before the onset of clinical disease and this prediabetic phase provides a potential opportunity to manipulate the islet-specific immune response to prevent or postpone β-cell loss. The latest developments in understanding the heterogeneity of T1DM and characterization of major disease subtypes might help in the development of preventive treatments.

Unsafe Drinking Water Is Associated with Environmental Enteric Dysfunction and Poor Growth Outcomes in Young Children in Rural Southwestern Uganda

Environmental enteric dysfunction (EED), a subclinical disorder of the small intestine, and poor growth are associated with living in poor water, sanitation, and hygiene (WASH) conditions, but specific risk factors remain unclear. Nested within a birth cohort study, this study investigates relationships among water quality, EED, and growth in 385 children living in southwestern Uganda. Water quality was assessed using a portable water quality test when children were 6 months, and safe water was defined as lacking Escherichia coli contamination. Environmental enteric dysfunction was assessed using the lactulose:mannitol (L:M) test at 12-16 months. Anthropometry and covariate data were extracted from the cohort study, and associations were assessed using linear and logistic regression models. Less than half of the households (43.8%) had safe water, and safe versus unsafe water did not correlate with improved versus unimproved water source. In adjusted linear regression models, children from households with safe water had significantly lower log-transformed (ln) L:M ratios (β: -0.22, 95% confidence interval (CI): -0.44, -0.00) and significantly higher length-for-age (β: 0.29, 95% CI: 0.00, 0.58) and weight-for-age (β: 0.20, 95% CI: 0.05, 0.34) Z-scores at 12-16 months. Furthermore, in adjusted linear regression models, ln L:M ratios at 12-16 months significantly decreased with increasing length-for-age Z-scores at birth, 6 months, and 9 months (β: -0.05, 95% CI: -0.10, -0.004; β: -0.06, 95% CI: -0.11, -0.006; and β: -0.05, 95% CI: -0.09, -0.005, respectively). Overall, our data suggest that programs seeking to improve nutrition should address poor WASH conditions simultaneously, particularly related to household drinking water quality.

Infant Nutritional Status, Feeding Practices, Enteropathogen Exposure, Socioeconomic Status, and Illness Are Associated with Gut Barrier Function As Assessed by the Lactulose Mannitol Test in the MAL-ED Birth Cohort

The lactulose mannitol (LM) dual sugar permeability test is the most commonly used test of environmental enteropathy in developing countries. However, there is a large but conflicting literature on its association with enteric infection and host nutritional status. We conducted a longitudinal cohort using a single field protocol and comparable laboratory procedures to examine intestinal permeability in multiple, geographically diverse pediatric populations. Using a previously published systematic review to guide the selection of factors potentially associated with LM test results, we examined the relationships between these factors and mucosal breach, represented by percent lactulose excretion; absorptive area, represented by percent mannitol excretion; and gut barrier function, represented by the L/M ratio. A total of 6,602 LM tests were conducted in 1,980 children at 3, 6, 9, and 15 months old; percent lactulose excretion, percent mannitol excretion, and the L/M ratio were expressed as age- and sex-specific normalized values using the Brazil cohort as the reference population. Among the factors considered, recent severe diarrhea, lower socioeconomic status, and recent asymptomatic enteropathogen infections were associated with decreased percent mannitol excretion and higher L/M ratios. Poorer concurrent weight-for-age, infection, and recent breastfeeding were associated with increased percent lactulose excretion and increased L/M ratios. Our results support previously reported associations between the L/M ratio and factors related to child nutritional status and enteropathogen exposure. These results were remarkably consistent across sites and support the hypothesis that the frequency of these exposures in communities living in poverty leads to alterations in gut barrier function.

Large Gliadin Peptides Detected in the Pancreas of NOD and Healthy Mice following Oral Administration

Gluten promotes type 1 diabetes in nonobese diabetic (NOD) mice and likely also in humans. In NOD mice and in non-diabetes-prone mice, it induces inflammation in the pancreatic lymph nodes, suggesting that gluten can initiate inflammation locally. Further, gliadin fragments stimulate insulin secretion from beta cells directly. We hypothesized that gluten fragments may cross the intestinal barrier to be distributed to organs other than the gut. If present in pancreas, gliadin could interact directly with the immune system and the beta cells to initiate diabetes development. We orally and intravenously administered 33-mer and 19-mer gliadin peptide to NOD, BALB/c, and C57BL/6 mice and found that the peptides readily crossed the intestinal barrier in all strains. Several degradation products were found in the pancreas by mass spectroscopy. Notably, the exocrine pancreas incorporated large amounts of radioactive label shortly after administration of the peptides. The study demonstrates that, even in normal animals, large gliadin fragments can reach the pancreas. If applicable to humans, the increased gut permeability in prediabetes and type 1 diabetes patients could expose beta cells directly to gliadin fragments. Here they could initiate inflammation and induce beta cell stress and thus contribute to the development of type 1 diabetes.

Heterogeneity in diabetes-associated autoantibodies and susceptibility to Type 1 diabetes: lessons for disease prevention

Autoantibodies against pancreatic islets are strong predictors of Type 1 diabetes. When persistent β-cell autoantibodies against at least two autoantigens are detected, the probability of diabetes is extremely high, although the time period before disease development can vary from days up to more than 20 years. Insulin autoantibodies or antibodies specific to glutamate decarboxylase 65 enzyme are in most cases, the first autoantibodies to appear. Insulin autoantibodies typically emerge very early with a peak at the age of 1.5 years, whereas the onset of glutamic acid decarboxylase 65 antibody positivity has a more even distribution, peaking later in childhood. These differences in the timing of appearance suggest that different environmental factors might be involved in the initiation of β-cell autoimmunity beginning either already in infancy or later on. This should be taken into account in studies aimed at identifying environmental factors triggering islet cell-specific autoimmunity and also in the design of prevention trials.

Gliadin fragments and a specific gliadin 33-mer peptide close KATP channels and induce insulin secretion in INS-1E cells and rat islets of langerhans

In non-obese diabetic (NOD) mice, diabetes incidence is reduced by a gluten-free diet. Gluten peptides, such as the compound gliadin, can cross the intestinal barrier and may directly affect pancreatic beta cells. We investigated the effects of enzymatically-digested gliadin in NOD mice, INS-1E cells and rat islets. Six injections of gliadin digest in 6-week-old NOD mice did not affect diabetes development, but increased weight gain (20% increase by day 100). In INS-1E cells, incubation with gliadin digest induced a dose-dependent increase in insulin secretion, up to 2.5-fold after 24 hours. A similar effect was observed in isolated rat islets (1.6-fold increase). In INS-1E cells, diazoxide reduced the stimulatory effect of gliadin digest. Additionally, gliadin digest was shown to decrease current through K_ATP-channels. A specific gliadin 33-mer had a similar effect, both on current and insulin secretion. Finally, INS-1E incubation with gliadin digest potentiated palmitate-induced insulin secretion by 13% compared to controls. Our data suggest that gliadin fragments may contribute to the beta-cell hyperactivity observed prior to the development of type 1 diabetes.

Interaction of enterovirus infection and cow's milk-based formula nutrition in type 1 diabetes-associated autoimmunity

BACKGROUND

Enteral virus infections and early introduction of cow's milk (CM)-based formula are among the suggested triggers of type 1 diabetes (T1D)-associated autoimmunity, although studies on their role have remained contradictory. Here, we aimed to analyse whether interactions between these factors might clarify the controversies.

MATERIALS

The study population comprised 107 subjects developing positivity for at least two T1D-associated autoantibodies and 446 control subjects from the Finnish diabetes prediction and prevention cohort. Enterovirus, rotavirus, adenovirus, respiratory syncytial virus and bovine insulin-binding antibodies were analysed from prospective serum samples at 3-24 months of age. Data on infant cow's milk exposure were available for 472 subjects: 251 subjects were exposed to cow's milk before 3 months of age and 221 subjects later in infancy.

RESULTS

Signs of an enterovirus infection by 12 months of age were associated with the appearance of autoimmunity among children who were exposed to cow's milk before 3 months of age. Cox regression analysis revealed a combined effect of enterovirus infection and early cow's milk exposure for the development of ICA and any of the biochemically defined autoantibodies (p = 0.001), of IAA (p = 0.002), GADA (p = 0.001) and IA-2A (p = 0.013).

CONCLUSIONS

The effect of enterovirus infection on the appearance of T1D-associated autoimmunity seems to be modified by exposure to cow's milk in early infancy suggesting an interaction between these factors. Moreover, these results provide an explanation for the controversial findings obtained when analysing the effect of any single one of these factors on the appearance of T1D-associated autoimmunity.

Is the origin of type 1 diabetes in the gut?

In type 1 diabetes, insulin-producing beta-cells in the pancreas are destroyed by immune-mediated mechanisms. The manifestation of the disease is preceded by the so-called pre-diabetic period that may last several years and is characterized by the appearance of circulating autoantibodies against beta-cell antigens. The role of the gut as a regulator of type 1 diabetes was suggested in animal studies, in which changes affecting the gut immune system modulated the incidence of diabetes. Dietary interventions, alterations in the intestinal microbiota and exposure to enteric pathogens, regulate the development of autoimmune diabetes in animal models. It has been demonstrated that these modulations affect the gut barrier mechanisms and intestinal immunity. Because the pancreas and the gut belong to the same intestinal immune system, the link between autoimmune diabetes and the gut is not unexpected. The gut hypothesis in the development of type 1 diabetes is also supported by the observations made in human type 1 diabetes. Early diet could modulate the development of beta-cell autoimmunity; weaning to hydrolysed casein formula decreased the risk of beta-cell autoimmunity by age 10 in the infants at genetic risk. Increased gut permeability, intestinal inflammation with impaired regulatory mechanisms and dysregulated oral tolerance have been observed in children with type 1 diabetes. The factors that contribute to these intestinal alterations are not known, but interest is focused on the microbial stimuli and function of innate immunity. It is likely that our microbial environment does not support the healthy maturation of the gut and tolerance in the gut, and this leads to the increasing type 1 diabetes as well as other immune-mediated diseases regulated by intestinal immune system. Thus, the interventions, aiming to prevent or treat type 1 diabetes in humans, should be targeting the gut immune system.

Type-specific human papillomavirus detection in cervical smears in Romania

To study type 1 diabetes (T1D), excellent animal models exist, both spontaneously diabetic and virus-induced. Based on knowledge from these, this review focuses on the environmental factors leading to T1D, concentrated into four areas which are: (1) The thymus-dependent immune system: T1D is a T cell driven disease and the beta cells are destroyed in an inflammatory insulitis process. Autoimmunity is breakdown of self-tolerance and the balance between regulator T cells and aggressive effector T cells is disturbed. Inhibition of the T cells (by e.g. anti-CD3 antibody or cyclosporine) will stop the T1D process, even if initiated by virus. Theoretically, the risk from immunotherapy elicits a higher frequency of malignancy. (2) The activity of the beta cells: Resting beta cells display less antigenicity and are less sensitive to immune destruction. Beta-cell rest can be induced by giving insulin externally in metabolic doses or by administering potassium-channel openers. Both procedures prevent T1D in animal models, whereas no good human data exist due to the risk of hypoglycemia. (3) NKT cells: According to the hygiene hypothesis, stimulation of NKT cells by non-pathogen microbes gives rise to less T cell reaction and less autoimmunity. Glycolipids presented by CD1 molecules are central in this stimulation. (4) Importance of the intestine and gliadin intake: Gluten-free diet dramatically inhibits T1D in animal models, and epidemiological data are supportive of such an effect in humans. The mechanisms include less subclinical intestinal inflammation and permeability, and changed composition of bacterial flora, which can also be obtained by intake of probiotics. Gluten-free diet is difficult to implement, and short-term intake has no effect. Regarding the onset of the T1D disease process, slow-acting enterovirus and gliadin deposits are speculated to be etiological in genetically susceptible individuals, followed by the mentioned four pathogenetic factors acting in concert. Neutralization of any one of these factors is capable of stopping T1D development, as lessons are learned from the animal models.

Multiple facets of intestinal permeability and epithelial handling of dietary antigens

The intestinal epithelium, the largest interface between the host and environment, regulates fluxes of ions and nutrients and limits host contact with the massive load of luminal antigens. Local protective and tolerogenic immune responses toward luminal content depend on antigen sampling by the gut epithelial layer. Whether, and how exaggerated, the entrance of antigenic macromolecules across the gut epithelium might initiate and/or perpetuate chronic inflammation as well as the respective contribution of paracellular and transcellular permeability remains a matter of debate. To this extent, experimental studies involving the in vivo assessment of intestinal permeability using small inert molecules do not necessarily correlate with the uptake of larger dietary antigens. This review analyzes both the structural and functional aspects of intestinal permeability with special emphasis on antigen handling in healthy and diseased states and consequences on local immune responses to food antigens.

The "perfect storm" for type 1 diabetes: the complex interplay between intestinal microbiota, gut permeability, and mucosal immunity

It is often stated that type 1 diabetes results from a complex interplay between varying degrees of genetic susceptibility and environmental factors. While agreeing with this principal, our desire is that this Perspectives article will highlight another complex interplay potentially associated with this disease involving facets related to the gut, one where individual factors that, upon their interaction with each another, form a "perfect storm" critical to the development of type 1 diabetes. This trio of factors includes an aberrant intestinal microbiota, a "leaky" intestinal mucosal barrier, and altered intestinal immune responsiveness. Studies examining the microecology of the gastrointestinal tract have identified specific microorganisms whose presence appears related (either quantitatively or qualitatively) to disease; in type 1 diabetes, a role for microflora in the pathogenesis of disease has recently been suggested. Increased intestinal permeability has also been observed in animal models of type 1 diabetes as well as in humans with or at increased-risk for the disease. Finally, an altered mucosal immune system has been associated with the disease and is likely a major contributor to the failure to form tolerance, resulting in the autoimmunity that underlies type 1 diabetes. Herein, we discuss the complex interplay between these factors and raise testable hypotheses that form a fertile area for future investigations as to the role of the gut in the pathogenesis and prevention of type 1 diabetes.

Changes in macromolecular transport appear early in Caco-2 cells infected with a human rotavirus

OBJECTIVE

Rotavirus is a major cause of viral gastroenteritis, but its interaction with intestinal mucosa is poorly understood. The aim of this study was to examine the effect of Wa rotavirus (VP7 serotype 1) on barrier function in confluent Caco-2 cell monolayers. Wa is the most common serotype causing severe diarrhoea in humans. MATERIAL AND METHODS. We examined light and electron microscopic morphology, macromolecular transport, paracellular permeability, electrical parameters, disaccharidases and cytoskeletal structure in Wa- and in control sham-infected cells using a homologous human virus-cell system resembling human infection.

RESULTS

During the first 48 h following Wa infection, there was no evidence of loss of integrity or of cytopathic effect in the monolayer. A significant cytopathic effect was noticed after 48 h. Further studies examined the initial 24-h period during which there was no evidence of significant injury. Apical-to-basolateral transcytosis of the macromolecule horseradish peroxidase (HRP) was selectively inhibited at 4 and 24 h post-infection with Wa. There were no significant changes in basolateral-to-apical transcytosis, endocytosis or in apical-to-apical recycling of HRP after Wa infection. G- and F-actin levels were significantly reduced within an area corresponding to the viroplasm in Wa-infected cells but not elsewhere in the monolayer.

CONCLUSIONS

The early stages of rotavirus infection, before gross epithelial injury, are associated with a selective reduction in the apical uptake and transcytosis of macromolecules. We speculate that this is an epithelial defence mechanism.

Enteral virus infections in early childhood and an enhanced type 1 diabetes-associated antibody response to dietary insulin

Enteral virus infections may trigger the development of beta-cell-specific autoimmunity by interacting with the gut-associated lymphoid system. We analyzed the effect of three different virus infections on immunization to dietary insulin in children carrying increased genetic risk for type 1 diabetes. Forty-six of 238 children developed multiple diabetes-associated autoantibodies and 31 clinical diabetes (median follow-up time 75 months). Insulin-binding antibodies were measured with EIA method (median follow-up time 24 months). Antibodies to enteroviruses, rotavirus and adenovirus were measured with EIA in samples drawn at birth and the ages of 3 and 6 months. Nineteen enterovirus, 14 rotavirus and 8 adenovirus infections were diagnosed. At the ages of 6, 12, and 18 months, the concentrations of insulin-binding antibodies were higher in children with postnatal entero-, rota- and/or adenovirus infections than in children without these infections. Children who subsequently developed ICA or IA-2 antibodies or clinical type 1 diabetes had higher concentrations of insulin-binding antibodies than children who remained autoantibody negative. Our data suggest that enteral virus infections can enhance immune response to insulin, induced primarily by bovine insulin in cow's milk. An enhanced antibody response to dietary insulin preceded the development of beta-cell specific autoimmunity and type 1 diabetes.

Gut barrier dysfunction in food allergy

Intestinal permeability tests used in the diagnosis of allergic diseases in response to oral food challenge have led to the conclusion that constitutive defects of the intestinal barrier are not the primary cause of allergic diseases. However, perturbation of environmental factors (infection, stress), by increasing intestinal permeability and enhancing danger signals, may favour food allergy in susceptible individuals. The mechanisms of enhanced permeability to specific and bystander antigens have been delineated as well as the molecular events involved in the sequential phases of allergic reactions. Intestinal absorption of food antigens and immune responses are mutually dependent, and luminal (environmental) and serosal (intrinsic) factors synergize to maintain a self-perpetuating cycle in which antigens penetrate the mucosa and induce allergic inflammation.

The rotavirus surface protein VP8 modulates the gate and fence function of tight junctions in epithelial cells

Rotaviruses constitute a major cause of diarrhea in young mammals. Rotaviruses utilize different integrins as cell receptors, therefore upon their arrival to the intestinal lumen their integrin receptors will be hidden below the tight junction (TJ), on the basolateral membrane. Here we have studied whether the rotavirus outer capsid proteins are capable of opening the paracellular space sealed by the TJ. From the outermost layer of proteins of the rotavirus, 60 spikes formed of protein VP4 are projected. VP4 is essential for virus-cell interactions and is cleaved by trypsin into peptides VP5 and VP8. Here we found that when these peptides are added to confluent epithelial monolayers (Madin-Darby canine kidney cells), VP8 is capable of diminishing in a dose dependent and reversible manner the transepithelial electrical resistance. VP5 exerted no effect. VP8 can also inhibit the development of newly formed TJs in a Ca-switch assay. Treatment with VP8 augments the paracellular passage of non-ionic tracers, allows the diffusion of a fluorescent lipid probe and the apical surface protein GP135, from the luminal to the lateral membrane, and triggers the movement of the basolateral proteins Na+-K+-ATPase, alphanubeta3 integrin and beta1 integrin subunit, to the apical surface. VP8 generates a freeze-fracture pattern of TJs characterized by the appearance of loose end filaments, that correlates with an altered distribution of several TJ proteins. VP8 given orally to diabetic rats allows the enteral administration of insulin, thus indicating that it can be employed to modulate epithelial permeability.

Parenteral immunization to beta-lactoglobulin modifies the intestinal structure and mucosal electrical parameters in rabbit

Systemic and local immune responses and the intestinal structure were examined in parenterally beta-Lg-sensitized rabbits. Immunization led to high IgG titers against beta-Lg. In a Ussing chamber, a sensitized ileum had a higher short-circuit current (Isc) and potential difference (PD) than a control following in vitro beta-Lg challenge. Histological study indicated that presence of the sensitizing antigen affected and considerably modified the structure of the intestinal mucosa in sensitized rabbits when compared to controls. These alterations were revealed by active atrophy and marked infiltration of the lymphocytes. These findings indicate that antigen exposure results in morphological changes and abnormalities affecting the transport of water and electrolytes. This study provides a clearer understanding of the physiopathological mechanisms of allergy to cow's milk protein.

Probiotics as modulators of the gut flora

Probiotic ingestion can be recommended as a preventative approach to maintaining the balance of the intestinal microflora and thereby enhance 'well-being'. Research into the use of probiotic intervention in specific illnesses and disorders has identified certain patient populations that may benefit from the approach. Undoubtedly, probiotics will vary in their efficacy and it may not be the case that the same results occur with all species. Those that prove most efficient will likely be strains that are robust enough to survive the harsh physico-chemical conditions present in the gastrointestinal tract. This includes gastric acid, bile secretions and competition with the resident microflora. A survey of the literature indicates positive results in over fifty human trials, with prevention/treatment of infections the most frequently reported output. In theory, increased levels of probiotics may induce a 'barrier' influence against common pathogens. Mechanisms of effect are likely to include the excretion of acids (lactate, acetate), competition for nutrients and gut receptor sites, immunomodulation and the formation of specific antimicrobial agents. As such, persons susceptible to diarrhoeal infections may benefit greatly from probiotic intake. On a more chronic basis, it has been suggested that some probiotics can help maintain remission in the inflammatory conditions, ulcerative colitis and pouchitis. They have also been suggested to repress enzymes responsible for genotoxin formation. Moreover, studies have suggested that probiotics are as effective as anti-spasmodic drugs in the alleviation of irritable bowel syndrome. The approach of modulating the gut flora for improved health has much relevance for the management of those with acute and chronic gut disorders. Other target groups could include those susceptible to nosocomial infections, as well as the elderly, who have an altered microflora, with a decreased number of beneficial microbial species. For the future, it is imperative that mechanistic interactions involved in probiotic supplementation be identified. Moreover, the survival issues associated with their establishment in the competitive gut ecosystem should be addressed. Here, the use of prebiotics in association with useful probiotics may be a worthwhile approach. A prebiotic is a dietary carbohydrate selectively metabolised by probiotics. Combinations of probiotics and prebiotics are known as synbiotics.

A similar high level of immunoglobulin A and immunoglobulin G class milk antibodies and increment of local lymphoid tissue on the duodenal mucosa in subjects with cow's milk allergy and recurrent abdominal pains

In previous studies, we have reported endoscopic and histological alterations locally on the gastrointestinal (GI) tract associated with a gastrointestinal type of cow's milk allergy. In this study, we sought to further characterize endoscopic, and immunological findings in these children. We also hypothesized that the same type of immune responses might also be found in children with unexplained and recurrent abdominal pains. We did a gastroduodenoscopy for persistent GI symptoms, examined the mucosal histology of the small intestine and measured the antibodies to whole cow's milk and its fractions with an enzyme-linked immunosorbent assay (ELISA) in a consecutive series of 22 subjects with untreated and 14 with treated cow's milk allergy (CMA) and 44 with recurrent abdominal pains (RAP). The immunological findings of the study subjects were compared with 54 controls. Lymphonodular hyperplasia (LNH) of the duodenum was the main endoscopic finding in 11 subjects (50%) with untreated and 5 (36%) with treated CMA. It was also found in 6 of 44 subjects with RAP. Compared with the controls, the patients with CMA showed significantly higher levels of IgA class antibodies to whole milk (p = 0.003) and betaLG (p < 0.0001). Of the IgG class antibodies to betaLG (p = 0.032), BSA (p < 0.0001) and alphaCAS (p < 0.0001) were significantly higher. The patients with LNH of the duodenal bulb as the main endoscopic finding showed significantly higher values of IgG class antibodies to betaLG (p = 0.01) and alphaCAS (p = 0.005). Interestingly, the patients examined for RAP showed a similar increment in the pattern of whole milk and specific milk protein antibodies as the CMA children. In conclusion this study showed that gastrointestinal CMA beyond infancy is significantly associated with high levels of IgG and IgA class antibodies to milk and its fractions. As high levels of these antibodies and LNH of the duodenal bulb were also found in subjects with RAP, the study further suggests that gastrointestinal CMA might be one major reason for RAP.

The gut immune system and type 1 diabetes

Accumulating data suggest that the gut immune system plays a role in the development of autoimmune diabetes: (1) Diet modifies the incidence of autoimmune diabetes and the phenotype of the islet-infiltrating T cells in the animal models of human type 1 diabetes; (2) gut-associated homing receptor beta7-integrin is found on the islet-infiltrating T cells in both human type 1 diabetes and in the animal models of autoimmune diabetes; (3) mesenterial lymphocytes from young NOD mice are able to transfer diabetes to healthy recipients; (4) autoantigen feeding modifies the disease development in the animal models (prevents or accelerates autoimmune diabetes). In humans, a link between the gut immune system and type 1 diabetes has also been suggested. Early introduction of cow milk formulas in infancy may increase the risk of type 1 diabetes. We have demonstrated that primary immunization to a beta cell-specific autoantigen, insulin, occurs in the gut by exposure to cow milk formulas, which contain immunogenic bovine insulin. The induced antibody and T cell responses to bovine insulin cross-react with human insulin. In children at genetic risk who developed beta cell autoimmunity, bovine insulin-binding antibodies increased during follow-up in contrast to autoantibody-negative children. This suggests that insulin-specific immune response induced by dietary insulin may not be controlled in children prone to beta cell autoimmunity. The gut immune system has a key role in controlling insulin-specific immunity induced by dietary insulin. Indeed, indications for aberrant function of the gut immune system have been reported in type 1 diabetes, such as intestinal immune activation and increased intestinal permeability. Research on the gut immune system in human type 1 diabetes is needed to reveal the role of oral immunity in this disease.

The role of the gut in beta-cell autoimmunity and type 1 diabetes: a hypothesis

The origin of autoimmunity leading to the destruction of insulin-producing beta-cells is not known. Several studies suggest that a link exists between the gut immune system and the islets infiltrating lymphocytes. Inflamed pancreatic islets express the same adhesion molecules involved with the homing of gut-associated lymphocytes. The manifestation of autoimmune diabetes in the animal models can be modified by dietary factors, which cause changes in the cytokine production by islet-infiltrating lymphocytes. Increased risk of type 1 diabetes has been associated with an early introduction of cows' milk formula in infancy, indicating that triggering of the gut immune system in early infancy may contribute to the later development of beta-cell autoimmunity. Enhanced immune reactivity to cow milk (CM) proteins in the patients with type 1 diabetes suggests aberrant regulation of the gut immune system in this disease. In the patients with newly diagnosed type 1 diabetes, anti-glutamate decarboxylase (GAD)-reactivity was found in the subpopulation of lymphocytes expressing gut-associated homing receptor alpha 4 beta 7. Based on these findings, the hypothesis that aberrant function of the gut immune system would lead to the development of beta-cell autoimmunity and type 1 diabetes has recently received a lot of attention. The possibility that regulation of the gut immune system is not normal in subjects at risk of autoimmune diabetes should be considered when treatments interfering with mucosal immunity for the prevention of type 1 diabetes are planned.

Rotavirus alters paracellular permeability and energy metabolism in Caco-2 cells

Rotaviruses infect epithelial cells of the small intestine, but the pathophysiology of the resulting severe diarrhea is incompletely understood. Histological damage to intestinal epithelium is not a consistent feature, and in vitro studies showed that intestinal cells did not undergo rapid death and lysis during viral replication. We show that rotavirus infection of Caco-2 cells caused disruption of tight junctions and loss of transepithelial resistance (TER) in the absence of cell death. TER declined from 300 to 22 Omega. cm(2) between 8 and 24 h after infection and was accompanied by increased transepithelial permeability to macromolecules of 478 and 4,000 Da. Distribution of tight junction proteins claudin-1, occludin, and ZO-1 was significantly altered during infection. Claudin-1 redistribution was notably apparent at the onset of the decline in TER. Infection was associated with increased production of lactate, decreased mitochondrial oxygen consumption, and reduced cellular ATP (60% of control at 24 h after infection), conditions known to reduce the integrity of epithelial tight junctions. In conclusion, these data show that rotavirus infection of Caco-2 intestinal cells altered tight junction structure and function, which may be a response to metabolic dysfunction.

Food protein-induced enterocolitis syndrome: laboratory perspectives

The expression of food protein allergy in man is very heterogeneous, varies with the age of the subject and is to a certain extent genetically determined. Skin prick tests with standardized food extracts are a sensitive method for detection of immunoglobulin E bound to reactive cells such as mast cells. Various tests on cellular immunity have been developed, especially because T-cell mediated reactions are considered to play a role in mainly delayed gastrointestinal reactions to cow's milk proteins. Food allergy may involve the entire gut, from mouth to rectum, including the esophagus. Abnormalities in intestinal permeability are the hallmarks of the inflamed gut, and may contribute to diagnosis of food induced enteropathy. What determines the characteristics of the intestinal inflammatory response is largely the cytokine responses triggered by the pathologic mechanism, whatever its origin, in the stomach, the small intestine, and the colon. A so-called T-helper type 2 response is characteristic of the allergic subject. A secretion of tumor necrosis factor-alpha alpha by blood cells of children allergic to milk was shown. All means of investigation may help in analyzing food substitutes for allergic infants.

Gut and the induction of immune tolerance in type 1 diabetes

The origin of beta-cell specific autoimmunity is not known in Type 1 diabetes. Several studies of this disease in animal models indicate that the manifestation of autoimmune diabetes can be modified by factors which influence the gut immune system. Some indirect evidence from studies in patients with Type 1 diabetes also suggests that aberrant function of the gut immune system may be involved in the development of this disease. These studies have encouraged the search for treatments interfering with mucosal immunity for the prevention of Type 1 diabetes. Our understanding of the function of the gut immune system in humans is, however, limited and the use of drugs (e.g. oral antigens or immune adjuvants) which modify the function of the gut immune system may involve serious problems. In this review, the possible role of the gut immune system in the development of beta-cell autoimmunity and Type 1 diabetes is discussed with special reference to the putative therapeutic implications.

Functional food science and gastrointestinal physiology and function

The gut is an obvious target for the development of functional foods, acting as it does as the interface between diet and the metabolic events which sustain life. The key processes in digestive physiology which can be regulated by modifying diet are satiety, the rate and extent of macronutrient breakdown and absorption from the small bowel, sterol metabolism, the colonic microflora, fermentation, mucosal function and bowel habit, and the gut immune system. The intestinal microflora is the main focus of many current functional foods. Probiotics are foods which contain live bacteria which are beneficial to health whilst prebiotics, such as certain non-digestible oligosaccharides which selectively stimulate the growth of bifidobacteria in the colon, are already on the market. Their claimed benefits are to alleviate lactose maldigestion, increase resistance to invasion by pathogenic species of bacteria in the gut, stimulate the immune system and possibly protect against cancer. There are very few reports of well-designed human intervention studies with prebiotics as yet. Certain probiotic species have been shown to shorten the duration of rotavirus diarrhoea in children but much more work is needed on the mechanism of immunomodulation and of competitive exclusion and microflora modification. The development of functional foods for the gut is in its infancy and will be successful only if more fundamental research is done on digestive physiology, the gut microflora, immune system and mucosal function.

Treatment of acute diarrhoea in practice

The recommended treatment for acute diarrhoea includes oral rehydration and rapid refeeding is increasingly recommended. The objective of this study was to assess the home use of oral rehydration, and rehydration and realimentation in hospital. The parents of children (aged less than 4 y) with acute diarrhoea answered questions on supplementary fluids and diet during the current diarrhoea at home (n = 129). The admitted patients (n = 60) were weighed daily and food consumption was measured (consecutive 3-d food record). Oral rehydration had been attempted in 67% of the children managed at the outpatient department and in 65% of those admitted. The total energy intake was on average 697 kcal (95% confidence interval 639-755), which is two-thirds of that recommended for the age group. Oral rehydration has become accepted in the management of acute diarrhoea, while rapid realimentation is not yet equally endorsed.

Cow-milk allergy

Hereditary predisposition is the major denominator of allergy, and hypersensitivity reactions contribute to the expression of the genetic predisposition. The route of sensitization varies with age so that dietary antigens predominate in infancy. The immaturity of the immune system and the gastrointestinal barrier may explain the peak prevalence of food allergies at an early age. The treatment of choice for cow-milk allergy is complete avoidance of cow-milk antigens. The approach to control allergic inflammation by antigen elimination, however, has not been satisfactory. New approaches are urgently needed for the management of patients with cow-milk allergy. These may include: (i) immunotherapy to counteract the immunological dysfunction, and (ii) stabilisation of the gut mucosal barrier to strengthen endogenous defence mechanisms.

Clinical uses of probiotics for stabilizing the gut mucosal barrier: successful strains and future challenges

Probiotic bacteria are used to treat disturbed intestinal microflora and increased gut permeability which are characteristic to many intestinal disorders. Examples include children with acute rotavirus diarrhoea, subjects with food allergy, subjects with colonic disorders and patients undergoing pelvic radiotherapy and sometimes changes associated with colon cancer development. In all such disease states altered intestinal microflora, impaired gut barrier and different types of intestinal inflammation are present. Successful probiotic bacteria are able to survive gastric conditions and colonize the intestine, at least temporarily, by adhering to the intestinal epithelium. Such probiotic microorganisms appear to be promising candidates for the treatment of clinical conditions with abnormal gut microflora and altered gut mucosal barrier functions. They are also promising ingredients to future functional foods and clinical foods for specific disease states provided that basic requirements for strains and clinical studies are carefully followed.

Increased frequency of IgM antibodies to cow's milk proteins in Hungarian children with newly diagnosed insulin-dependent diabetes mellitus

We investigated the association between serum antibodies to cow's milk proteins and insulin-dependent diabetes mellitus (IDDM) in Hungarian children. Forty-eight children 1.0-17.1 years of age with newly diagnosed IDDM and 74 control children 1.0-16.0 years of age were studied for serum IgG, IgA and IgM antibodies to cow's milk, beta-lactoglobulin, bovine serum albumin and ovalbumin by enzyme-linked immunosorbent assays. The specificity of IgM antibodies to beta-lactoglobulin and bovine serum albumin was controlled by Western blot. The levels of IgG and IgA antibodies to cow's milk proteins were similar in children with and without IDDM, with the exception of slightly increased levels of IgA antibodies to beta-lactoglobulin in diabetic children (P = 0.05). The levels of IgM antibodies to cow's milk were significantly higher in IDDM patients than in control children (P = 0.0002). Children with IDDM more often had IgM antibodies to beta-lactoglobulin (46.3% vs 18.8%; P = 0.002) and bovine serum albumin (87.8% vs 49.3%, P < 0.0001) than control children. Neither the levels of IgG or IgA antibodies to ovalbumin nor the frequency of IgM antibodies to ovalbumin differed between diabetic and control children.

CONCLUSION

In Hungarian children, clinical manifestation of IDDM is often associated with IgM antibody response to cow's milk protein and its fractions, beta-lactoglobulin and bovine serum albumin, indicating a loss of immunological tolerance to these proteins. IgG and IgA antibodies to cow's milk proteins, associated with an early introduction of cow's milk in diet, seem to play a minor role in the development of childhood IDDM in Hungary.

Enhanced absorption of macromolecules. A secondary factor in Crohn's disease

We explored the function of the intestine's mucosal barrier to foreign antigen entry in Crohn's disease. Macroscopically and microscopically uninvolved areas of the small intestines of patients with Crohn's disease were examined. We studied 27 endoscopic biopsy samples from 17 patients with Crohn's disease and 14 samples from nine controls. The absorption and degradation of horseradish peroxidase (molecular weight 40,000 Da) were studied in Ussing chambers. The absorption of intact horseradish peroxidase was significantly increased in patients with moderate or severe Crohn's disease: 271 (95% confidence interval 119-616) ng/hr/cm2, but not in those with slight disease activity: 42 (18-98), compared with controls: 45 (32-64); F = 10.90, P = 0.0002. The transport rates of degraded horseradish peroxidase were comparable in the Crohn's disease samples and controls. Our results indicate that enhanced absorption of macromolecules is associated with clinical activation of Crohn's disease, and impairment of the mucosal barrier function is a secondary phenomenon in Crohn's disease.

Gut permeability to human alpha-lactalbumin, beta-lactoglobulin, mannitol, and lactulose in celiac disease

Our objective was to examine the permeability of the gut to protein macromolecules and sugar probes and their possible association in celiac disease patients. We studied the permeability to human alpha-lactalbumin, beta-lactoglobulin, mannitol, and lactulose on 46 occasions in 33 celiac disease patients in various phases of the disease; in addition, mannitol and lactulose permeability was studied in 18 healthy controls. Lactalbumin absorption was detected in 19 of 42 patients tested, more often in celiac disease patients with villous atrophy than in those with normal jejunal biopsy (p = 0.01). Higher absorption of lactalbumin was found in patients with subtotal villous atrophy than in those with normal biopsy (p = 0.02). beta-lactoglobulin was found in four of 42 patients tested. Less mannitol was absorbed by patients with either subtotal or partial villous atrophy than by those with normal histology (p = 0.001 and 0.006, respectively). Lactulose recovery was higher in newly diagnosed patients and patients with subtotal villous atrophy than in controls (p = 0.007 and 0.03, respectively). The lactulose/mannitol ratio was higher in newly diagnosed patients and patients with villous atrophy than in controls (p = 0.002 and 0.002, respectively). The correlation between permeability to lactalbumin and mannitol and lactulose was poor. We conclude that permeability to proteins and sugar molecules is abnormal in celiac disease patients with mucosal damage and that they probably reflect different mechanisms of penetration.

Oral bacteriotherapy for viral gastroenteritis

The effect of orally administered lactobacilli on acute rotavirus diarrhea was tested in 42 well-nourished children ages 5-28 months. After oral rehydration, the patients were randomized to a study group, receiving human Lactobacillus casei strain GG 10(10) colony-forming units twice daily for five days, or a control group not given lactobacilli. Lactobacillus GG was found in the feces in 83% of the study group. The diarrheal phase was shortened in that group. Dietary supplementation with lactobacilli significantly influenced the bacterial enzyme profile: urease activity during diarrhea transiently increased in the control group but not in the study group; F = 8.6, P = 0.01. No intergroup differences were found in beta-glucuronidase, beta-glucosidase, and glycocholic acid hydrolase levels. We suggest that rotavirus infection gives rise to biphasic diarrhea, the first phase being an osmotic diarrhea and the second associated with overgrowth of specifically urease-producing bacteria. Oral bacteriotherapy appears a promising means to counteract the disturbed microbial balance.

Development of mucosal immune function in man: potential for GI disease states

The human mucosal immune system is structurally mature and has all the necessary cellular components to generate an immune response at birth. However, in the absence of dietary antigens and bacterial flora, there are no secondary follicles in the Peyer's patches and virtually no immunoglobulin A plasma cells in the lamina propria. Reactive follicle centers develop after birth but it takes 2 years for mucosal IgA plasma cell density to reach adult levels. T cells are present in the epithelium and lamina propria at birth, albeit at a lower frequency than later in life and there are major differences in phenotype between T cells in fetal intestine and postnatal intestine. There is no information on the impact of the massive antigenic challenge at birth on the mucosal immune system. Well-documented deficiencies in the ability of the blood T cells of the neonate to produce interleukin-4 and interferon-gamma may also occur in the intestine. It is still an open question whether it is better to try to prevent immunological sensitization of the newborn by avoiding potential allergens (i.e. cow's milk), or whether early exposure (as happens when premature infants are given formula feeds) might tolerize the infant. Hydrolysed cow's milk formulae are probably less antigenic than whole cow's milk and have been widely used in the treatment of cow's milk allergy. Some thought is now being given as to whether the prophylactic use of hydrolysates can reduce cow's milk allergy in 'at-risk' infants.

Lack of immune responsiveness to bovine serum albumin in insulin-dependent diabetes

BACKGROUND

Epidemiologic studies have implicated the ingestion of cow's milk in the pathogenesis of insulin-dependent diabetes mellitus (IDDM). Moreover, in a recent study, 100 percent of patients with new-onset IDDM had antibodies against bovine serum albumin (BSA), with a majority directed against a 17-amino-acid BSA peptide (ABBOS). Cellular immune mechanisms are thought to be the principal mediators of pancreatic beta-cell destruction in IDDM.

METHODS

We measured the responses of peripheral-blood mononuclear cells to BSA and ABBOS or serum IgG anti-BSA antibodies (by particle-concentration fluorescence immunoassay) in 71 patients with IDDM, 55 subjects at various degrees of risk for IDDM, 36 patients with other autoimmune disorders (chronic autoimmune thyroiditis, rheumatoid arthritis, and systemic lupus erythematosus), and 48 normal subjects.

RESULTS

The responses of peripheral-blood mononuclear cells to BSA or ABBOS were positive in 2 of 24 patients with new-onset IDDM, 1 of 25 first-degree relatives of patients with IDDM who were negative for islet-cell antibodies, 2 of 30 first-degree relatives of patients with IDDM who were positive for islet-cell antibodies, 1 of 28 patients with established IDDM, and 1 of 29 normal subjects. Similarly, anti-BSA antibodies were not detected significantly more often in patients with new-onset IDDM (3 of 31, 10 percent) than in normal subjects (1 of 37, 3 percent; P = 0.32). However, many patients with autoimmune disease and subjects at increased risk for IDDM had anti-BSA antibodies (frequency, 10 to 31 percent).

CONCLUSIONS

Anti-BSA antibodies may reflect a general defect in the process of immunologic tolerance associated with a predisposition to autoimmunity rather than immunity specific to beta cells. The absence of cellular immunity to BSA and ABBOS in IDDM does not support a role for this antigen in the pathogenesis of the disorder.

Intestinal permeability in pediatric gastroenterology

The role of the physiologic barrier function of the small bowel and its possible role in health and disease has attracted much attention over the past decade. The intestinal mucosal barrier for luminal macromolecules and microorganism is the result of non-immunologic and immunologic defense mechanisms. The non-immunologic mechanisms consist of intraluminal factors such as gastric acid, proteolytic activity, and motility and of mucosal surface factors like mucin and the microvillous membrane. The immunologic mechanisms include secretary IgA and cell-mediated immunity. Both types of mechanism are not completely mature at birth. Maturation of this barrier is not finished before the 2nd year of life. One of the aspects of the mucosal barrier function can be estimated by the intestinal permeability (IP) for macromolecules. We use the differential sugar absorption test (SAT), in which the ratio of urinary excretion of a relatively large molecule, lactulose, is compared with that of a relatively small molecule, mannitol, after oral ingestion. Although the small intestine is permeable to certain macromolecules in normal developmental conditions, an increased IP could be involved in the pathophysiology of several diseases, including infectious diarrhea, food allergy, celiac disease, and Crohn's disease. It can be concluded that IP, as measured with the SAT, reflects the state of the mucosal barrier and is altered in several gastrointestinal diseases. The SAT is a non-invasive IP test that can be of diagnostic help to demonstrate alterations in the small-mucosal barrier function and may be useful to evaluate therapeutic interventions.(ABSTRACT TRUNCATED AT 250 WORDS)