Increased intestinal permeability precedes clinical onset of type 1 diabetes

The potential role of glutamate in the current diabetes epidemic

In the present article, we propose the perspective that abnormal glutamate homeostasis might contribute to diabetes pathogenesis. Previous reports and our recent data indicate that chronically high extracellular glutamate levels exert direct and indirect effects that might participate in the progressive loss of β-cells occurring in both T1D and T2D. In addition, abnormal glutamate homeostasis may impact all the three accelerators of the "accelerator hypothesis" and could partially explain the rising frequency of T1D and T2D.

What is the key environmental trigger in type 1 diabetes--is it viruses, or wheat gluten, or both?

Prevention and treatment of type 1 diabetes is hampered by the fact that the key environmental trigger(s) of the disease is still unknown. Much of the data on this subject points to two possibilities, viruses and wheat gluten. Viruses appear to be involved as an etiological agent in some cases of type 1 diabetes, particularly in fulminant type 1 diabetes. Further analysis of the data suggests that viruses are not the sole trigger of type 1 diabetes in humans, and that wheat gluten may play a role in initiating the disease. Viruses may be the key environmental trigger in some cases of type 1 diabetes, and wheat gluten in others. Conceivably, some cases of type 1 diabetes might be caused by viruses and wheat gluten acting together as disease triggers.

The influence of the microbiota on type-1 diabetes: on the threshold of a leap forward in our understanding

The last several years have seen breakthroughs in techniques to track the symbiont communities that normally colonize mammals (the microbiota) and in cataloguing the universe of the genes they carry (the microbiome). Applying these methods to human patients and corresponding murine models should allow us to decipher just how the microbiota impacts type-1 diabetes, i.e. which particular microbes are responsible and the cellular and molecular processes that are involved. Here, at its threshold, we set the stage for what promises to be an exciting rejuvenated area of investigation.

Impact of dietary gluten on regulatory T cells and Th17 cells in BALB/c mice

Dietary gluten influences the development of type 1 diabetes (T1D) and a gluten-free (GF) diet has a protective effect on the development of T1D. Gluten may influence T1D due to its direct effect on intestinal immunity; however, these mechanisms have not been adequately studied. We studied the effect of a GF diet compared to a gluten-containing standard (STD) diet on selected T cell subsets, associated with regulatory functions as well as proinflammatory Th17 cells, in BALB/c mice. Furthermore, we assessed diet-induced changes in the expression of various T cell markers, and determined if changes were confined to intestinal or non-intestinal lymphoid compartments. The gluten-containing STD diet led to a significantly decreased proportion of γδ T cells in all lymphoid compartments studied, although an increase was detected in some γδ T cell subsets (CD8⁺, CD103⁺). Further, it decreased the proportion of CD4⁺CD62L⁺ T cells in Peyer's patches. Interestingly, no diet-induced changes were found among CD4⁺Foxp3⁺ T cells or CD3⁺CD49b⁺cells (NKT cells) and CD3⁻CD49b⁺ (NK) cells. Mice fed the STD diet showed increased proportions of CD4⁺CD45RB^high+ and CD103⁺ T cells and a lower proportion of CD4⁺CD45RB^low+ T cells in both mucosal and non-mucosal compartments. The Th17 cell population, associated with the development of autoimmunity, was substantially increased in pancreatic lymph nodes of mice fed the STD diet. Collectively, our data indicate that dietary gluten influences multiple regulatory T cell subsets as well as Th17 cells in mucosal lymphoid tissue while fewer differences were observed in non-mucosal lymphoid compartments.

Do interactions between gut ecology and environmental chemicals contribute to obesity and diabetes?

BACKGROUND

Gut microbiota are important factors in obesity and diabetes, yet little is known about their role in the toxicodynamics of environmental chemicals, including those recently found to be obesogenic and diabetogenic.

OBJECTIVES

We integrated evidence that independently links gut ecology and environmental chemicals to obesity and diabetes, providing a framework for suggesting how these environmental factors may interact with these diseases, and identified future research needs.

METHODS

We examined studies with germ-free or antibiotic-treated laboratory animals, and human studies that evaluated how dietary influences and microbial changes affected obesity and diabetes. Strengths and weaknesses of studies evaluating how environmental chemical exposures may affect obesity and diabetes were summarized, and research gaps on how gut ecology may affect the disposition of environmental chemicals were identified.

RESULTS

Mounting evidence indicates that gut microbiota composition affects obesity and diabetes, as does exposure to environmental chemicals. The toxicology and pharmacology literature also suggests that interindividual variations in gut microbiota may affect chemical metabolism via direct activation of chemicals, depletion of metabolites needed for biotransformation, alteration of host biotransformation enzyme activities, changes in enterohepatic circulation, altered bioavailability of environmental chemicals and/or antioxidants from food, and alterations in gut motility and barrier function.

CONCLUSIONS

Variations in gut microbiota are likely to affect human toxicodynamics and increase individual exposure to obesogenic and diabetogenic chemicals. Combating the global obesity and diabetes epidemics requires a multifaceted approach that should include greater emphasis on understanding and controlling the impact of interindividual gut microbe variability on the disposition of environmental chemicals in humans.

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.

Nutritional therapy in practice for learning, behavioural and mood disorders

There is an evidential link between diet, mood and behaviour, but a shortage of formalised educational literature covering the role of nutritional science and its application in the care and treatment of mental health problems. In the U.K., a limited amount of a few types of fruit and vegetables, few wholegrains and little oily fish are consumed. Instead, large quantities of refined carbohydrates, altered fats, intensively reared meat and dairy products are eaten, along with unknown combinations of synthetic chemicals and residues. In some individuals, specific nutritional and environmental factors generate physiological responses which may influence mood, promote anti-social behaviour and trigger overwhelming cravings for certain foods or substances. Nutritional Therapists are not currently part of the multidisciplinary team assessing people suffering from mental health problems. They generally work in private practice with clients on an individual basis. Their role is to improve diet and identify potential food intolerances, hormone imbalances, blood sugar issues, enzyme deficiencies, compromised gut immunity, increased nutrient requirements, a toxic metal burden or chemical sensitivities. Each case is examined on its own merits, given the variety of genetic and environmental differences among individuals. The considerable challenge for the nutritional therapist remains to intervene safely and effectively in mental health conditions which involve multiple complex and interacting mechanisms.

Sensitization to gliadin induces moderate enteropathy and insulitis in nonobese diabetic-DQ8 mice

Celiac disease (CD) is frequently diagnosed in patients with type 1 diabetes (T1D), and T1D patients can exhibit Abs against tissue transglutaminase, the auto-antigen in CD. Thus, gliadin, the trigger in CD, has been suggested to have a role in T1D pathogenesis. The objective of this study was to investigate whether gliadin contributes to enteropathy and insulitis in NOD-DQ8 mice, an animal model that does not spontaneously develop T1D. Gliadin-sensitized NOD-DQ8 mice developed moderate enteropathy, intraepithelial lymphocytosis, and barrier dysfunction, but not insulitis. Administration of anti-CD25 mAbs before gliadin-sensitization induced partial depletion of CD25(+)Foxp3(+) T cells and led to severe insulitis, but did not exacerbate mucosal dysfunction. CD4(+) T cells isolated from pancreatic lymph nodes of mice that developed insulitis showed increased proliferation and proinflammatory cytokines after incubation with gliadin but not with BSA. CD4(+) T cells isolated from nonsensitized controls did not response to gliadin or BSA. In conclusion, gliadin sensitization induced moderate enteropathy in NOD-DQ8 mice. However, insulitis development required gliadin-sensitization and partial systemic depletion of CD25(+)Foxp3(+) T cells. This humanized murine model provides a mechanistic link to explain how the mucosal intolerance to a dietary protein can lead to insulitis in the presence of partial regulatory T cell deficiency.

Lower expression of tight junction protein 1 gene and increased FOXP3 expression in the small bowel mucosa in coeliac disease and associated type 1 diabetes mellitus

BACKGROUND

The role of regulatory T cells expressing FOXP3 in the pathogenesis of coeliac disease (CD) and type 1 diabetes (T1D) has been reported. Recent data have placed special focus on the interplay between the intestinal barrier and immunoregulatory processes. We aimed to determine whether the expression of tight junction protein 1 (TJP1), which reflects small bowel mucosa permeability, is changed in CD and T1D.

METHODS

Transcription levels of TJP1 and FOXP3 genes were evaluated in the small bowel biopsies of 14 children with CD, 12 with CD and coexisting T1D and 40 controls using real-time PCR. Serum IgA and IgG to deamidated gliadin, bovine β-lactoglobulin, bovine α-casein and human tissue transglutaminase (tTG) were determined by ELISA.

RESULTS

The highest expression of FOXP3 mRNA was seen in patients with CD and T1D compared to patients with CD alone and controls (p = 0.02). In contrast, the lowest level of TJP1 mRNA expression was found in patients with CD and T1D (p = 0.01). The levels of IgA to deamidated gliadin and tTG were highest in patients with CD and T1D (p = 0.0001 and 0.01, respectively). The expression of FOXP3 mRNA correlated highly with the level of anti-gliadin IgA (p = 0.02) and anti-tTG IgA antibodies (p = 0.004).

CONCLUSION

The significant decline in TJP1 expression in CD patients, particularly in those with coexisting T1D, was accompanied by an increase in FOXP3 expression. This might reflect an attempt to maintain immune tolerance to counterbalance the loss of mucosal integrity in the small intestine in CD associated with T1D.

The gut as a regulator of early inflammation in type 1 diabetes

PURPOSE OF REVIEW

Several studies indicate that factors affecting the gut are capable of modulating the development of autoimmune diabetes. This review discusses the recent research on these mechanisms, which may reveal novel pathogenic pathways and new possibilities for prevention of type 1 diabetes (T1D).

RECENT FINDINGS

The role of the gut as a regulator of T1D is mainly based on animal studies in which changes affecting the gut immune system have been shown to modulate the immune-mediated destruction of insulin-producing beta-cells. Dietary interventions, alterations in the intestinal microbiota and exposure to enteral pathogens regulate the development of autoimmune diabetes in animal models. In several studies, it has been demonstrated that these modulations affect the gut barrier mechanisms and intestinal immunity. Also, in humans, increased gut permeability and intestinal inflammation are associated with T1D. A recent report of dietary intervention study in infants at genetic risk of T1D showed that early diet could modulate the development of beta-cell autoimmunity in humans; weaning to hydrolyzed casein formula decreased the risk of beta-cell autoimmunity by age 10.

SUMMARY

The gut modulation affecting permeability, inflammation and microbiota is evidently associated with the regulation of the inflammation leading to beta-cell destruction. Although the mechanisms of action are not fully understood, the recent research points out the lines of approach for the prevention of T1D.

Defective differentiation of regulatory FoxP3+ T cells by small-intestinal dendritic cells in patients with type 1 diabetes

OBJECTIVE

The gut environment modulates the pathogenesis of type 1 diabetes (T1D), but how it affects autoimmunity toward pancreatic β-cells, a self-tissue located outside the intestine, is still unclear. In the small intestine, lamina propria dendritic cells (LPDCs) induce peripheral differentiation of FoxP3(+) regulatory T (Treg) cells. We tested the hypothesis that the intestinal milieu impinges on human T1D by affecting differentiation of FoxP3(+) Treg cells.

RESEARCH DESIGN AND METHODS

We collected duodenal biopsies of 10 T1D patients, 16 healthy subjects, and 20 celiac individuals and performed a fluorescent-activated cell sorter analysis to measure percentages of various immune cell subsets, including CD4(+) and CD8(+) T cells, NK cells, γδ T cells, CD103(+)CD11c(+) LPDCs, and CD4(+)CD25(+)FoxP3(+)CD127(-) Treg cells. In parallel, we assessed the tolerogenic function (i.e., capacity to induce differentiation of FoxP3(+) Treg cells) by LPDCs of T1D patients and control subjects.

RESULTS

Our analysis revealed a significant reduction in the percentage of intestinal CD4(+)CD25(+)FoxP3(+)CD127(-) Treg cells in T1D patients compared with healthy subjects (P = 0.03) and celiac individuals (P = 0.003). In addition, we found that LPDCs from T1D patients completely lacked their tolerogenic function; they were unable to convert CD4(+)CD25(-) T cells into CD4(+)CD25(+)FoxP3(+)CD127(-) Treg cells.

CONCLUSIONS

Our data indicate that T1D patients have a reduced number of intestinal FoxP3(+) Treg cells as a result of their defective differentiation in the gut. These findings suggest that intestinal immune regulation is not only calibrated to tolerate commensal bacteria and food components but also is instrumental in maintaining immune tolerance toward pancreatic β-cells and preventing T1D.

Leaky gut and diabetes mellitus: what is the link?

Diabetes mellitus is a chronic disease requiring lifelong medical attention. With hundreds of millions suffering worldwide, and a rapidly rising incidence, diabetes mellitus poses a great burden on healthcare systems. Recent studies investigating the underlying mechanisms involved in disease development in diabetes point to the role of the dys-regulation of the intestinal barrier. Via alterations in the intestinal permeability, intestinal barrier function becomes compromised whereby access of infectious agents and dietary antigens to mucosal immune elements is facilitated, which may eventually lead to immune reactions with damage to pancreatic beta cells and can lead to increased cytokine production with consequent insulin resistance. Understanding the factors regulating the intestinal barrier function will provide important insight into the interactions between luminal antigens and immune response elements. This review analyses recent advances in the mechanistic understanding of the role of the intestinal epithelial barrier function in the development of type 1 and type 2 diabetes. Given our current knowledge, we may assume that reinforcing the intestinal barrier can offer and open new therapeutic horizons in the treatment of type 1 and type 2 diabetes.

Insulin autoantibodies with high affinity to the bovine milk protein alpha casein

Insulin autoantibodies (IAA) can appear in children within months of introducing solid foods to the diet and before clinical type 1 diabetes. The aim of this study was to determine whether infant dietary antigens could be immunizing agents of IAA. To this end, IAA binding to [(125) I]insulin was competed with food preparations and extracts of foods encountered in the infant diet (milk formulas, bovine milk, wheat flour, fowl meal). Bovine milk powder extracts inhibited IAA-positive samples from six of 53 children (age 0·3-14·0 years) participating in German prospective cohorts. Inhibition in these sera ranged from 23 to 100%. Competition was abolished when hydrolyzed milk powder was used. Competition with protein components of bovine milk found that two of the six milk-reactive sera were inhibited strongly by alpha- and beta-casein; none were inhibited by the milk proteins bovine serum albumin or lactoglobulins. The two casein-reactive sera had high affinity to alpha-casein (1·7×10(9) ; 3·1×10(9)  l/mol), and lesser affinity to beta-casein (4·0×10(8) ; 7·0×10(7)  l/mol) and insulin (2·6×10(8) ; 1·6×10(8)  l/mol). No children with milk-reactive IAA developed autoantibodies to other islet autoantigens or diabetes (median follow-up 9·8 years). These results suggest that autoimmunity to insulin can occur infrequently via cross-reactivity to food proteins, but this form of IAA immunization does not appear to be associated with progression to diabetes.

Celiac disease in patients with type 1 diabetes: a condition with distinct changes in intestinal immunity?

Two common chronic childhood diseases-celiac disease (CD) and type 1 diabetes (T1D)-result from complex pathological mechanisms where genetic susceptibility, environmental exposure, alterations in intestinal permeability and immune responses play central roles. In this study, we investigated whether these characteristics were universal for CD independently of T1D association. For this purpose, we studied 36 children with normal small-bowel mucosa and 26 children with active CD, including 12 patients with T1D. In samples from the small-bowel mucosa, we detected the lowest expression of tight junction protein 1 (TJP1) mRNA in CD patients with T1D, indicating an increase in intestinal permeability. Furthermore, these samples displayed the highest expression of forkhead box P3 (FoxP3) mRNA, a marker for regulatory T cells, as compared with other patient groups. At the same time, serum levels of IgA antibodies specific for the CD-related antigens deamidated gliadin and tissue transglutaminase (tTG) were the highest in CD patients with T1D. In contrast, no significant differences were found in IgA or IgG antibodies specific for bovine beta-lactoglobulin or Bifidobacterium adolescentis DSM 20083-derived proteins. There were also no differences in the transamidating activity of serum autoantibodies between patients and control individuals. Our results show that patients with T1D and newly detected CD exhibit severely altered intestinal permeability, strong local immune activation and increased immunoregulatory mechanisms in the small bowel. Further study is required to determine whether these extreme changes in this CD subgroup are due to some specific environmental factors (virus infections), unknown genetic effects or autoimmune reactions to antigenic targets in intracellular tight junctions.

The changing epidemiology of type 1 diabetes: why is it going through the roof?

The incidence of type 1 diabetes is increasing and this may double the burden of disease in our youngest by 2020. The recent increase in incidence is mostly happening in the very young and those with moderate genetic susceptibility. Many environmental factors have been implicated, but no major determinants have been clearly identified, and the mechanisms of involvement remain elusive. This review summarizes current research efforts directed at understanding the possible reasons for this increase, including the role of viruses, gut microbiota, early life feeding patterns, perinatal factors and childhood growth patterns. It also provides a road map for future research directions.

Antibodies to the wheat storage globulin Glo-3A in children before and at diagnosis of celiac disease

OBJECTIVE

Celiac disease (CD) is an autoimmune disease triggered by exposure to gluten-containing foods. IgA autoantibodies to tissue transglutaminase (TTG) are elevated in CD, but little is known about the gastrointestinal state before the appearance of TTG. Antibodies to wheat storage globulin Glo-3A have been studied in type 1 diabetes, and may be a marker of altered mucosal barrier and/or immune function. In the present study, we investigated antibody responses to Glo-3A in CD.

PATIENTS AND METHODS

In the Diabetes Autoimmunity Study in the Young, children were studied prospectively from birth for the appearance of TTG and CD. Fifty cases of CD were frequency matched with 50 controls on age (of TTG seroconversion in the case), sex, ethnicity, presence of a first-degree relative with type 1 diabetes mellitus, and human leukocyte antigen -DR3 genotype. In cases and controls, IgG antibodies to Glo-3A were analyzed in a blinded manner in the sample collected at the time of seroconversion to TTG positivity (or the matched sample in controls) and in all of the previous samples since birth (mean 4.5 samples). The association between Glo-3A antibody levels and CD case status was explored using t tests at the TTG-positive visit and when Glo-3A levels were highest, and mixed modeling to describe Glo-3A over time.

RESULTS

At the time of first elevated TTG (mean 4.9 years), patients with CD had higher Glo-3A antibody levels than controls (13.3 ± 17.2 vs 7.6 ± 11.7, P = 0.005). In both cases and controls, Glo-3A antibodies appear to peak at a mean age of 2.9 years, before mean age of initial TTG seroconversion. The peak Glo-3A antibody levels were higher in cases than controls (25.5 ± 21.8 vs 14.9 ± 18.3 P = 0.0007). Using mixed modeling to account for multiple visits per person, cases had higher levels of Glo-3A antibodies than controls at all ages from birth to TTG seroconversion (β = 0.53, P = 0.002).

CONCLUSIONS

Compared with controls, CD cases have higher Glo-3A antibody responses in the beginning years, before initial detection of TTG.

Restoration of impaired intestinal barrier function by the hydrolysed casein diet contributes to the prevention of type 1 diabetes in the diabetes-prone BioBreeding rat

AIMS/HYPOTHESIS

Impaired intestinal barrier function is observed in type 1 diabetes patients and animal models of the disease. Exposure to diabetogenic antigens from the intestinal milieu due to a compromised intestinal barrier is considered essential for induction of the autoimmune process leading to type 1 diabetes. Since a hydrolysed casein (HC) diet prevents autoimmune diabetes onset in diabetes-prone (DP)-BioBreeding (BB) rats, we studied the role of the HC diet on intestinal barrier function and, therefore, prevention of autoimmune diabetes onset in this animal model.

METHODS

DP-BB rats were fed the HC diet from weaning onwards and monitored for autoimmune diabetes development. Intestinal permeability was assessed in vivo by lactulose-mannitol test and ex vivo by measuring transepithelial electrical resistance (TEER). Levels of serum zonulin, a physiological tight junction modulator, were measured by ELISA. Ileal mRNA expression of Myo9b, Cldn1, Cldn2 and Ocln (which encode the tight junction-related proteins myosin IXb, claudin-1, claudin-2 and occludin) and Il-10, Tgf-ß (also known as Il10 and Tgfb, respectively, which encode regulatory cytokines) was analysed by quantitative PCR.

RESULTS

The HC diet reduced autoimmune diabetes by 50% in DP-BB rats. In DP-BB rats, prediabetic gut permeability negatively correlated with the moment of autoimmune diabetes onset. The improved intestinal barrier function that was induced by HC diet in DP-BB rats was visualised by decreasing lactulose:mannitol ratio, decreasing serum zonulin levels and increasing ileal TEER. The HC diet modified ileal mRNA expression of Myo9b, and Cldn1 and Cldn2, but left Ocln expression unaltered.

CONCLUSIONS/INTERPRETATION

Improved intestinal barrier function might be an important intermediate in the prevention of autoimmune diabetes by the HC diet in DP-BB rats. Effects on tight junctions, ileal cytokines and zonulin production might be important mechanisms for this effect.

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.

Inflammatory tendencies and overproduction of IL-17 in the colon of young NOD mice are counteracted with diet change

OBJECTIVE

Dietary factors influence diabetes development in the NOD mouse. Diet affects the composition of microbiota in the distal intestine, which may subsequently influence intestinal immune homeostasis. However, the specific effects of antidiabetogenic diets on gut immunity and the explicit associations between intestinal immune disruption and type 1 diabetes onset remain unclear.

RESEARCH DESIGN AND METHODS

Gut microbiota of NOD mice fed a conventional diet or ProSobee formula were compared using gas chromatography. Colonic lamina propria immune cells were characterized in terms of activation markers, cytokine mRNA and Th17 and Foxp3(+) T-cell numbers, using real-time PCR and flow cytometry. Activation of diabetogenic CD4 T-cells by purified B-cells was assessed in both groups. Immune tolerance to autologous commensal bacteria was evaluated in vitro using thymidine-incorporation tests.

RESULTS

Young NOD mice showed a disturbed tolerance to autologous commensal bacteria. Increased numbers of activated CD4 T-cells and (CD11b(+)CD11c(+)) dendritic cells and elevated levels of Th17 cells and IL23 mRNA were moreover observed in colon lamina propria. These phenomena were abolished when mice were fed an antidiabetogenic diet. The antidiabetogenic diet also altered the expression levels of costimulatory molecules and the capacity of peritoneal B-cells to induce insulin-specific CD4 T-cell proliferation.

CONCLUSIONS

Young NOD mice show signs of subclinical colitis, but the symptoms are alleviated by a diet change to an antidiabetogenic diet. Disrupted immune tolerance in the distal intestine may influence peritoneal cell pools and B-cell-mediated activation of diabetogenic T-cells.

The intestinal microbiome: relationship to type 1 diabetes

This article discusses recent evidence that associates the developing intestinal microbiome to the pathogenesis of autoimmune T1D. It attempts to identify avenues that should be pursued that relate this new evidence to interventions that eventually could result in prevention.

IL-17 immunity in human type 1 diabetes

Th17 immunity has been shown to regulate autoimmune diabetes in mice. IL-17 neutralization prevented development of diabetes when given postinitiation of insulitis but not earlier, suggesting interference with the effector phase of the disease. Islet-cell Ag-specific Th17 cells converted into IFN-gamma-secreting Th1-like cells and caused diabetes in mice recipients. The role of IL-17 in human type 1 diabetes (T1D) is, however, not established. In this study, we show upregulation of Th17 immunity in peripheral blood T cells from children with T1D. This was characterized by increased IL-17 secretion and expression of IL-17, IL-22, and retinoic acid-related orphan receptor C isoform 2, but also FOXP3 transcripts upon T cell activation in vitro. Also, circulating memory CD4 cells from children with T1D showed the same pattern of IL-17, IL-22 and FOXP3 mRNA upregulation, indicating IL-17 pathway activation in vivo. IL-17-positive T cells appeared to be CD4(+) cells expressing TCR-alphabeta and CCR6, and a subpopulation showed coproduction of IFN-gamma. Given the Th17 immunity in T1D, we demonstrated that IL-17 had detrimental effects on human islet cells in vitro; it potentiated both inflammatory and proapoptotic responses. Our findings highlight the role of IL-17 immunity in the pathogenesis of human T1D and point to a potential therapeutic strategy.

Anti-Saccharomyces cerevisiae antibodies are frequent in type 1 diabetes

Anti-Saccharomyces cerevisiae antibodies (ASCA) have been described in many autoimmune diseases in which there is an increased intestinal permeability. Also in type 1 diabetes (T1D), there is an increased intestinal permeability. Since no data are available about ASCA in T1D, we evaluated, retrospectively, the frequency of ASCA in this disease. ASCA, IgG, and IgA, were determined by ELISA in sera of 224 T1D patients in which coeliac disease has been excluded and 157 healthy control group. The frequency of ASCA (IgG or IgA) was significantly higher in T1D patients than in the control group (24.5% vs. 2.5%, p < 10(-7)). The same observation was found in children and in adult patients when we compare them to healthy children and blood donors group respectively. Compared to children, adult patients with T1D showed significantly higher frequencies of ASCA of any isotype (38% vs. 13.7%, p < 10(-4)), both ASCA IgG and IgA (12% vs. 1.6%, p = 0.002), ASCA IgG (35% vs. 9.8%, p < 10(-5)) and ASCA IgA (15% vs. 5.6%, p = 0.001). The frequency of ASCA was statistically higher in females of all T1D than in males (30.8% vs.17.7%, p = 0.03), in girls than in boys (22% vs.6.2%, p = 0.017), and significantly higher in men than in boys (35.7% vs. 6.2%, p < 10(-4)). The frequency of ASCA IgG was significantly higher than that of ASCA IgA in all T1D patients (21% vs. 9.8%, p < 0.002), in all females (26.5% vs. 10.2%, p < 0.002), in women (37.9% vs. 12%, p < 0.001). The frequency of ASCA was significantly higher in all long-term T1D than in an inaugural T1D (29% vs. 14.5%, p = 0.019). The same observation was found in adults (45.8% vs. 17.8%, p = 0.01). In long-term T1D patients, ASCA were significantly more frequent in adults than children (45.8% vs. 14.5%, p < 10(-4)). The frequency of ASCA IgG was significantly higher in long-term T1D than in an inaugural T1D (25.2% vs. 11.6%, p = 0.03). Patients with T1D had a high frequency of ASCA.

Gut barrier disruption by an enteric bacterial pathogen accelerates insulitis in NOD mice

AIMS/HYPOTHESIS

Increased exposure to enteric microbes as a result of intestinal barrier disruption is thought to contribute to the development of several intestinal inflammatory diseases; however, it less clear whether such exposure modulates the development of extra-intestinal inflammatory and autoimmune diseases. The goal of this study was to examine the potential role of pathogenic enteric microbes and intestinal barrier dysfunction in the pathogenesis of type 1 diabetes.

METHODS

Using NOD mice, we assessed: (1) intrinsic barrier function in mice at different ages by measuring serum levels of FITC-labelled dextran; and (2) the impact on insulitis development of infection by strains of an enteric bacterial pathogen (Citrobacter rodentium) either capable (wild-type) or incapable (lacking Escherichia coli secreted protein F virulence factor owing to deletion of the gene [DeltaespF]) of causing intestinal epithelial barrier disruption.

RESULTS

Here we demonstrate that prediabetic (12-week-old) NOD mice display increased intestinal permeability compared with non-obese diabetes-resistant and C57BL/6 mice. We also found that young (4-week-old) NOD mice infected with wild-type C. rodentium exhibited accelerated development of insulitis in concert with infection-induced barrier disruption. In contrast, insulitis development was not altered in NOD mice infected with the non-barrier-disrupting DeltaespF strain. Moreover, C. rodentium-infected NOD mice demonstrated increased activation and proliferation of pancreatic-draining lymph node T cells, including diabetogenic CD8(+) T cells, compared with uninfected NOD mice.

CONCLUSIONS/INTERPRETATION

This is the first demonstration that a loss of intestinal barrier integrity caused by an enteric bacterial pathogen results in the activation of diabetogenic CD8(+) T cells and modulates insulitis.

An exploration of Glo-3A antibody levels in children at increased risk for type 1 diabetes mellitus

AIMS

To determine whether Glo-3A, (formerly referred to as homologue of Glb1 or Glb1) antibodies are associated with islet autoimmunity (IA) in children at increased risk for type 1 diabetes (T1D) and to investigate their relation with environmental correlates of T1D.

METHODS

We selected a sample from the Diabetes Autoimmunity Study in the Young (DAISY), a prospective study of children at increased risk for T1D. Cases were positive for insulin, glutamic acid decarboxylase (GAD), or insulinoma-associated antigen-2 (IA-2) autoantibodies on two consecutive visits and either diagnosed with diabetes mellitus or still autoantibody positive when selected. Controls were from the same increased risk group, of similar age as the cases but negative for autoantibodies. Sera from 91 IA cases and 82 controls were analyzed in a blinded manner for immunoglobulin G (IgG) antibodies to Glo-3A by ELISA.

RESULTS

Adjusting for family history of T1D and human leukocyte antigen (HLA)-DR4 positivity, Glo-3A antibodies were not associated with IA case status (OR: 1.01, 95% CI: 0.99-1.03). Adjusting for age, family history of T1D, and HLA-DR4 positivity, Glo-3A antibody levels were inversely associated with breast-feeding duration (beta = -0.08, p = 0.001) and directly associated with current intake of foods containing gluten (beta = 0.24, p = 0.007) in IA cases but not in controls. Zonulin, a biomarker of gut permeability, was directly associated with Glo-3A antibody levels in cases (beta = 0.73, p = 0.003) but not in controls.

CONCLUSION

Differing correlates of Glo-3A antibodies in IA cases and controls suggest an underlying difference in mucosal immune response.

Intestinal microflora and metabolic diseases

Recent advances in molecular sequencing technology have allowed researchers to answer major questions regarding the relationship between a vast genomic diversity-such as found in the intestinal microflora-and host physiology. Over the past few years, it has been established that, in obesity, type 1 diabetes and Crohn's disease-to cite but a few-the intestinal microflora play a pathophysiological role and can induce, transfer or prevent the outcome of such conditions. A few of the molecular vectors responsible for this regulatory role have been determined. Some are related to control of the immune, vascular, endocrine and nervous systems located in the intestines. However, more important is the fact that the intestinal microflora-to-host relationship is bidirectional, with evidence of an impact of the host genome on the intestinal microbiome. This means that the ecology shared by the host and gut microflora should now be considered a new player that can be manipulated, using pharmacological and nutritional approaches, to control physiological functions and pathological outcomes. What now remains is to demonstrate the molecular connection between the intestinal microflora and metabolic diseases. We propose here that the proinflammatory lipopolysaccharides play a causal role in the onset of metabolic disorders.

Glucagon-like peptide-2 reduces intestinal permeability but does not modify the onset of type 1 diabetes in the nonobese diabetic mouse

The development of type 1 diabetes (T1D) has been linked to environmental factors and dietary components. Increasing evidence indicates that the integrity of the gut mucosa plays a role in the development of autoimmune diseases, and evidence from both preclinical and clinical studies demonstrates that increased leakiness of the intestinal epithelium precedes the development of type 1 diabetes. However, there is limited information on modulation of gut barrier function and its relationship to diabetes development. Here we show that the nonobese diabetic (NOD) mouse, a model of T1D, exhibits enhanced intestinal transcellular permeability before the development of autoimmune diabetes. Treatment of NOD mice with a glucagon-like peptide 2 (GLP-2) analog, synthetic human [Gly(2)] glucagon-like peptide-2 (h[Gly(2)]GLP-2, increased the length and weight of the small bowel and significantly improved jejunal transepithelial resistance. However, chronic administration of once daily h[Gly(2)]GLP-2 failed to delay or reverse the onset of T1D when treatment was initiated in young, normoglycemic female NOD mice. Furthermore, h[Gly(2)]GLP-2 administration had no significant effect on lymphocyte subpopulations in NOD mice. These findings demonstrate that h[Gly(2)]GLP-2-mediated enhancement of gut barrier function in normoglycemic NOD mice disease is not sufficient to prevent or delay the development of experimental T1D.

The measurement and clinical significance of intestinal permeability

This article discusses the concept of intestinal permeability and the barrier function of the gut, elaborates on tight junction structure and the dynamic nature of its composition, outlines the methods for evaluating intestinal permeability, and explores abnormal intestinal permeability in clinical disease, emphasizing its possible role in the pathogenesis of autoimmune conditions. Evidence is provided from several representative diseases for a proposed model of abnormal intestinal permeability in autoimmune disease, including a description of a molecular pathway involving a signaling protein called zonulin, which appears to regulate intestinal permeability. Finally, we speculate on mechanisms that may be responsible for increasing intestinal permeability and consider clinical implications.

MAGI2 genetic variation and inflammatory bowel disease

BACKGROUND

Despite recent advances the majority of inflammatory bowel disease (IBD) susceptibility 'genes' remain undiscovered. Recent data suggest that autoimmune conditions may 'share' susceptibility loci. Epidemiological evidence indicates an association between celiac disease and IBD and both conditions demonstrate increased gut permeability. MAGI2, recently implicated in ulcerative colitis (UC) and celiac disease, encodes a scaffolding protein involved in epithelial integrity. Our aim was to test MAGI2 variants for association with IBD and also their role in determining intermediate hereditary phenotypes defined by antibody production to microbial antigens.

METHODS

We genotyped 113 MAGI2 single nucleotide polymorphisms (SNPs) in 681 cases of Crohn's disease (CD), 259 UC cases, and 195 controls.

RESULTS

The most significant IBD association was in intron 6 (rs2160322, P = 0.009) and both UC (P = 0.006) and CD (P = 0.03) contributed to this association. The most significant CD association was with an intron 2 haplotype (rs7785088/rs323149/rs13246026, P = 0.002). We observed highly significant associations with UC in intron 6 (rs7803276/rs7803705, P = 0.002) and also significant associations in introns 2, 6, and 20. Significant associations were seen with: immunoglobulin G (IgG) anti-Saccharomyces cerevisiae antibodies (ASCA)-positive CD in intron 3 (P = 0.003), intron 6 (P = 0.003), and intron 20 (P = 0.001); anti-CBir1-positive CD in intron 3 (P = 0.0001) and intron 6 (P = 0.008); and anti-outer membrane porin C (OmpC)-positive CD in intron 3 (P = 0.0009), and intron 9 (P = 0.007). Quantitative antibody levels were also associated with variants in intron 4 (anti-IgA ASCA, P = 0.0003 and anti-IgG ASCA, P = 0.0002).

CONCLUSIONS

These findings support the significance of the epithelial barrier in IBD pathogenesis.

Leaking gut in type 1 diabetes

PURPOSE OF REVIEW

Several studies have indicated that children with type 1 diabetes show altered intestinal immune system and, in particular, increased small intestinal permeability. This review discusses the recent research linking the gut and type 1 diabetes, which may reveal novel pathogenic pathways and new possibilities for disease prevention.

RECENT FINDINGS

Recent studies indicate that not only patients with manifest type 1 diabetes show increased small intestinal permeability and high serum levels of zonulin, that is protein controlling epithelial tight junctions, but prediabetic, normoglycemic individuals with beta-cell autoimmunity show signs of leaking gut. Also studies in BioBreeding-rat model of autoimmune diabetes suggest that high permeability of the intestine precedes autoimmune diabetes. The enteropathy characterized by increased intestinal permeability and inflammation seems to be the basis for the development of beta-cell destruction, as for example zonulin agonist, which decreases the gut permeability, prevents the development of diabetes.

SUMMARY

The leaking gut syndrome with subclinical inflammation is associated with beta-cell autoimmunity and type 1 diabetes. Furthermore, treatment of the leakiness has been reported to modulate development of autoimmune diabetes in animal models suggesting that intestinal environment plays a key role in the destruction of insulin-producing beta-cells in the pancreas.

Enhanced levels of cow's milk antibodies in infancy in children who develop type 1 diabetes later in childhood

BACKGROUND

Early exposure to cow's milk (CM) proteins have been implicated in the pathogenesis of type 1 diabetes (T1D).

OBJECTIVE

We analyzed the development of the humoral immune response to dietary CM proteins in early childhood and its relation to later T1D.

SUBJECTS AND METHODS

We studied a subgroup of 94 children randomized to be weaned to a CM-based infant formula in the trial to reduce insulin-dependent diabetes mellitus in the genetically at risk (TRIGR) pilot study. All subjects carried human leukocyte antigen-conferred T1D susceptibility and had an affected first-degree relative. After 7 years of follow-up, 8 subjects had progressed to T1D, 15 had at least one disease-associated autoantibody, and 71 remained autoantibody negative (controls). Immunoglobulin (Ig) G and IgA class antibodies to whole CM formula, beta-lactoglobulin (BLG), bovine serum albumin, and alpha-casein and IgG antibodies to bovine insulin (BI) were measured with enzyme-linked immunosorbent assays from sequential samples.

RESULTS

The children with later T1D showed increased IgG levels to BLG from 3 to 18 months of age (p = 0.028) and enhanced IgA levels to CM formula at the age of 9 months (p = 0.022) compared with controls. In the children with an affected father or sibling, IgG antibodies to BI were higher in autoantibody-positive subjects than in autoantibody-negative subjects at 18 months of age (p = 0.022).

CONCLUSION

An enhanced humoral immune response to various CM proteins in infancy is seen in a subgroup of those children who later progress to T1D. Accordingly, a dysregulated immune response to oral antigens is an early event in the pathogenesis of T1D.

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.

The intestine as a regulator of cholesterol homeostasis in diabetes

The chylomicron influences very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) composition but itself is atherogenic. Thus abnormalities of chylomicron production are of interest particularly in conditions such as diabetes which confer major cardiovascular risk. Intestinal function is abnormal in diabetes and is a major cause of the dyslipidaemia found in this condition. Studies have suggested that cholesterol absorption is decreased in diabetes and cholesterol synthesis increased. Molecular mechanisms involved in insulin resistance in the intestine and its effect on cholesterol homeostasis in diabetes are described. Abnormalities in triglyceride synthesis and alterations genes regulating cholesterol absorption and intestinal synthesis are discussed. In particular, increase in apolipoprotein B48 synthesis has been demonstrated in animal models of diabetes and insulin resistance. Intestinal mRNA expression of Niemann Pick C1-like 1, protein is increased in both experimental and human diabetes suggesting that an increase in cholesterol transportation does occur. mRNA expression of the ATP binding cassette proteins (ABC) G5 and G8, two proteins working in tandem to excrete cholesterol have been shown to be decreased suggesting increased delivery of cholesterol for absorption. Expression of microsomal triglyceride transfer protein, which assembles the chylomicron particle, is increased in diabetes leading to increase in both number and cholesterol content. In conclusion, diabetes is associated with considerable dysfunction of the intestine leading to abnormal chylomicron composition which may play a major part in the premature development of atherosclerosis.

A unifying hypothesis on the development of type 1 diabetes and celiac disease: gluten consumption may be a shared causative factor

This paper presents a hypothesis of the aetiology of the increasing incidence of type 1 diabetes (T1D). This together with the global increased incidence of celiac disease (CD) and that these increases cannot be explained by genetic factors suggest a common environmental factor for these two diseases. Even though enterovirus (EV) infections are believed to trigger T1D and gluten is the trigger of CD, the increasing intake of gluten containing products all over the world could be the trigger for both diseases directly and indirectly. It has been shown that the duration of exposure to gluten is related to the prevalence of T1D. It has also been shown that T1D patients at onset have an inflammatory reaction in the gut. Hence, early diagnose of CD followed by elimination of dietary gluten will lead to a decreased incidence of T1D.

Detection of enteroviruses in the intestine of type 1 diabetic patients

Enterovirus infections have been diagnosed more frequently in type 1 diabetic patients than in the healthy population, and enteroviruses have also been found in the pancreas of diabetic patients. Primary replication of the virus occurs in the gut, but there are no previous studies evaluating possible presence of virus in the intestine of diabetic patients. The purpose of this study was to investigate if enteroviruses can be found in small intestinal tissue of type 1 diabetic patients. Formalin-fixed, paraffin-embedded upper intestinal biopsy samples were analysed for the presence of enterovirus using in situ hybridization and immunohistochemistry. Enterovirus was detected by in situ hybridization in six (50%) of the type 1 diabetic patients (n = 12) but in none of the control subjects (n = 10, P = 0.015). Immunohistochemistry identified enterovirus in nine (75%) of the patients and one (10%) control subject (P = 0.004). The presence of the virus was confirmed by reverse transcription-polymerase chain reaction in one of the four patients from whom a frozen and unfixed sample was available. Intestinal morphology was normal in all study subjects. The results suggest that a substantial proportion of type 1 diabetic patients have an ongoing enterovirus infection in gut mucosa, possibly reflecting persistent enterovirus infection. This observation opens new avenues for further studies on the possible role of enteroviruses in human type 1 diabetes.