Cow's milk and type I diabetes: the gut immune system deserves attention

Functional significance of the rare rs35667974 IFIH1 gene polymorphism, associated with multiple autoimmune diseases, using a structural biological approach

Autoimmune diseases, which affect approximately 5% of human population, are a range of diseases in which the immune response to self-antigens results in damage or dysfunction of tissues. Recent genome wide association studies (GWAS) have successfully identified novel autoimmune disease-associated loci, with many of them shared by multiple disease-associated pathways but much of the genetics and pathophysiological mechanisms remain still obscure. Considering that most of the potential causal variants are still unknown, many studies showed that the missense variant rs35667974 at interferon-induced with helicase C domain 1 (IFIH1) gene is protective for type 1 diabetes (T1D), psoriasis (PS) and psoriatic arthritis (PsA). Recently, this variant was found to be also associated with ankylosing spondylitis (AS), Crohn's disease (CD) and ulcerative colitis (UC). The IFIH1 gene encodes a cytoplasmic RNA helicase otherwise known as melanoma differentiation-associated 5 (MDA5) that recognizes viral RNA and is involved in innate immunity through recognition of viral RNA. In the present study we sought to investigate the association of the rare rs35667974 variant of IFIH1 gene, which resides in exon 14 and changes a conserved isoleucine at position #923 to valine, in the development of various autoimmune diseases and give a reason for the selectivity affecting different autoimmune diseases. Evolutionary studies and three-dimensional (3 D) homology modelling were employed on the MDA5 protein product, through its association with dsRNA, recognition factor controlling cytokine and chemokine signalling, to investigate the protective role of the MDA5 variant for certain autoimmune diseases.

Environmental Factors as Diabetic Mediators: A Mechanistic Approach

Despite substantial investment in research and treatment options, diabetes mellitus remains a pressing public health concern with potential epidemic proportions globally. There are reports that by the end of 2040, 642 million people will be suffering from diabetes. Also, according to an estimation, 1.6 million deaths were caused directly by diabetes in 2016. Diabetes is a metabolic disorder characterized by impaired glucose regulation in the body due to the destruction of pancreatic β-cells or insulin resistance. Genetic propensity, unhealthy and imbalanced diet, obesity and increasing urbanization are the common risk factors for diabetes. Besides this, it has been reported that environmental pollutants like organic pesticides, heavy metals, and air pollutants act as strong predisposing factors for diabetes owing to their highly bio-accumulative nature. These pollutants disturb glucose homeostasis either by up-regulating or down-regulating the expression of diabetic marker genes like insulin (INS) and glucokinase (GCK). Unfortunately, the molecular mechanism of the role of pollutants in causing diabetes is not very clear. This mechanistic review provides evidence of different environmental determinants, including persistent organic pollutants (POPs), air pollutants, toxic metals, etc., in inducing diabetes and proposes a framework for the possible mechanisms involved. It also illuminates the current status and future challenges, which will not only broaden our understanding but can also be a reasonable platform for further investigation.

The Role of Exposomes in the Pathophysiology of Autoimmune Diseases I: Toxic Chemicals and Food

Autoimmune diseases affect 5–9% of the world’s population. It is now known that genetics play a relatively small part in the pathophysiology of autoimmune disorders in general, and that environmental factors have a greater role. In this review, we examine the role of the exposome, an individual’s lifetime exposure to external and internal factors, in the pathophysiology of autoimmune diseases. The most common of these environmental factors are toxic chemicals, food/diet, and infections. Toxic chemicals are in our food, drink, common products, the air, and even the land we walk on. Toxic chemicals can directly damage self-tissue and cause the release of autoantigens, or can bind to human tissue antigens and form neoantigens, which can provoke autoimmune response leading to autoimmunity. Other types of autoimmune responses can also be induced by toxic chemicals through various effects at the cellular and biochemical levels. The food we eat every day commonly has colorants, preservatives, or packaging-related chemical contamination. The food itself may be antigenic for susceptible individuals. The most common mechanism for food-related autoimmunity is molecular mimicry, in which the food’s molecular structure bears a similarity with the structure of one or more self-tissues. The solution is to detect the trigger, remove it from the environment or diet, then repair the damage to the individual’s body and health.

Evidences for diabetes and insulin mimetic activity of medicinal plants: Present status and future prospects

Diabetes mellitus (DM) is a considerable systemic metabolic disorder to exhibit various metabolic and cardiovascular disorders, mainly hyperglycemia. The global projected estimate of diabetes in 2030 will be about 439 million adults, out of which 300 million expected are of type-2 diabetes mellitus (T2DM). The present knowledge revealed responsible factors, occurrence and mechanism of these factors involved in the DM diseases. Hence, the aim of this review is to address and summarize the causes, plant resources, importance, present status and future programmes for diabetes control. The present review answers the contemporary present questions raised in the scientific field on DM. Two major problems are explained in detail about the autoimmune attack or dysfunction of β-cell and insulin resistance involved for Type 1 and Type 2 DM, respectively. Though there are various approaches to reduce the ill effects of diabetes and its secondary complications, many preferred herbal formulations due to lesser side effects and low cost. For this reason still it is getting increased attention in searching antidiabetic medicinal plants for hot research and to develop targeted medicine. Recurrence of islet autoimmunity lesson from pancreatic islet cell transplantation to cure T1D was outlined. With these highlights, the review summarizes the current knowledge on diabetes occurrence, factors (environmental and genetics), and types (I, II, gestation, and secondary DM), antidiabetic plants, sources for insulin mimetic plant principle compounds and their target mechanism with current and future trusted research areas for controlling of DM.

Type 1 diabetes and gut microbiota: Friend or foe?

Type 1 diabetes is a T cell-mediated autoimmune disease. Environmental factors play an important role in the initiation of the disease in genetically predisposed individuals. With the improved control of infectious disease, the incidence of autoimmune diseases, particularly type 1 diabetes, has dramatically increased in developed countries. Increasing evidence suggests that gut microbiota are involved in the pathogenesis of type 1 diabetes. Here we focus on recent advances in this field and provide a rationale for novel therapeutic strategies targeting gut microbiota for the prevention of type 1 diabetes.

The prevalence of antibodies against wheat and milk proteins in blood donors and their contribution to neuroimmune reactivities

The aim of this study was to look for the presence of IgG, IgM, and IgA antibodies against two widely consumed foods, wheat and milk, in a relatively large number of specimens. As wheat, milk, and their antigens have been found to be involved in neuroimmune disorders, we measured the co-occurrence of their antibodies against various neural antigens. We assessed the reactivity of sera from 400 donors to wheat and milk proteins, GAD-65, cerebellar, MBP, and MOG. Statistical analysis showed significant clustering when certain wheat and milk protein antibodies were cross-referenced with neural antibodies. Approximately half of the sera with antibody elevation against gliadin reacted significantly with GAD-65 and cerebellar peptides; about half of the sera with elevated antibodies against α + β-casein and milk butyrophilin also showed antibody elevation against MBP and MOG. Inhibition studies showed that only two out of four of the samples with elevated cerebellar or MOG antibodies could be inhibited by gliadin or α + β-casein, confirming individual variation in epitope recognition. We conclude that a subgroup of blood donors, due to a breakdown in immunological tolerance, may react and produce significant levels of antibodies (p-values less than 0.05) against wheat and milk antigens that cross-react with different neural antigens, which may have broader implications in the induction of neuroimmune reactivities.

Why is type 1 diabetes increasing?

A series of studies have reported a constant global rise in the incidence of type 1 diabetes. Epidemiological and immunological studies have demonstrated that environmental factors may influence the pathogenesis, leading to a cell-mediated pancreatic β-cell destruction associated with humoral immunity. The search for the triggering factor(s) has been going on for the past century, and yet they are still unknown. This review provides an overview of some of the most well-known theories found in the literature: hygiene, viral, vitamin D deficiency, breast milk and cow's milk hypotheses. Although the hygiene hypothesis appears to be the most promising, positive evidence from animal, human and epidemiological studies precludes us from completely discarding any of the other hypotheses. Moreover, due to contrasting evidence in the literature, a single factor is unlikely to cause an increase in the incidence of diabetes all over the world, which suggests that a multifactorial process might be involved. Although the immunological mechanisms are still unclear, there seems to be some overlap between the various hypotheses. It is thought that the emphasis should be shifted from a single to a multifactorial process and that perhaps the 'balance shift' model should be considered as a possible explanation for the rise in the incidence of type 1 diabetes.

Interaction of early diet and the development of the immune system

The present review focuses on the specific effects of nutrients on the development of the immune system in early life. There is a big gap regarding the specific mechanisms that regulate immunity at the intestinal level and their impact in the systemic immune function. For this reason, during the last few years there has been great interest in ascertaining the mechanisms that regulate the intestinal immune function, as well as to understand how specific nutrients interact with the gut-associated lymphoid tissue. We have reviewed this topic with special emphasis on how human milk, and its components, influence the early development of intestinal immunity in breast-fed infants compared with formula-fed infants. Interactions between nutrients and intestinal microbiota have also been reviewed. Some micronutrients such as nucleotides and gangliosides, which are present in human milk and also in most foods, are able to influence immune functionality at very low concentrations. The specific action of these micronutrients on some parameters of immunity, as well as their potential mechanisms of action, have been considered in detail. However, there are limited data on how other specific nutrients, namely protein and non-protein N-containing compounds, lipids, carbohydrates, and others, such as minerals, vitamins, fibre, non-nutritional dietary compounds (flavonoids, carotenoids, phyto-oestrogens, etc), influence immunity. In the present review we have provided data regarding the potential effects of these compounds on the immune response in early life. The increasing use of functional foods by the public to improve their general health and prevent the incidence of chronic diseases has become a major area of interest within the nutrition community. Of the many functional foods available, probiotics have been most studied in infancy and childhood, particularly with regard to the prevention of allergic diseases. Infant formulae and fermented milks containing large quantities of probiotics are produced and consumed by Europeans and in other industrialized countries. In the present review we cover the clinical effects of probiotics in preventing disease during early life, as well as the potential mechanisms of interaction between probiotics and the gastrointestinal tract.

Combinations of common chronic paediatric diseases deviate the immune response in diverging directions

The cytokine pattern of T lymphocytes has not been characterized in children with combinations of paediatric immunological disorders. We describe cytokine secretion in children with type 1 diabetes, coeliac disease and allergy and combinations of two of these diseases after stimulation with 'disease-specific' antigens. Peripheral blood mononuclear cells (PBMC) were collected from 68 children with type 1 diabetes, allergy or coeliac disease, two of these diseases in combination or none of these diseases. Using the enzyme-linked immunospot (ELISPOT) technique, interferon (IFN)-gamma and interleukin (IL)-4 were analysed from fresh PBMC spontaneously and after in vitro stimulation with antigens associated with one or more of these diseases (insulin, gluten, birch and cat extract, beta-lactoglobulin, ovalbumin and phytohaemagglutinin) in order to divide T helper (Th)1- from Th2-like lymphocytes. Stimulation with birch and cat extract caused increased IL-4 secretion in allergic children. A low IFN-gamma response to insulin was found in type 1 diabetic children, whereas allergic children responded to insulin by increased IL-4 secretion. Children suffering from both type 1 diabetes (Th1-prone) and allergy (Th2-prone) reacted distinctly to general mitogen stimulation. Children suffering from two Th1-dominated diseases (type 1 diabetes and coeliac disease) showed hardly any response to either food or inhalation allergens. Our results indicate an important interplay between common immunological diseases in children. The combination of two Th1-deviated diseases is associated with a suppressed immune response, whereas a combination of Th1- and Th2-dominated diseases appears to increase the general immune response.

Dietary proteins as environmental modifiers of type 1 diabetes mellitus

Type 1 diabetes is an autoimmune disease in which the patient's immune system destroys the insulin-secreting beta-cells in the pancreatic islets of Langerhans. A majority of cases is thought to occur as a result of gene-environment interactions. The identity of the environmental factors remains unknown mainly because of the difficulty in linking past exposures with later disease development. Overall, the data suggest a model in which individuals develop diabetes by several different pathways, each influenced by numerous genetic and environmental variables. The most investigated environmental factors are diet and viruses. In this review, we examine the evidence that the source of dietary proteins can modify diabetes outcome, describe new approaches to identify candidate diabetes-related dietary agents, examine possible links with gut dysfunction, discuss some of the limitations, and propose a multifactorial model for dietary modification of diabetes. The key to diabetes pathogenesis, its prevention, and the ultimate success of beta-cell replacement therapies lies in understanding how the environment controls disease expression. Dietary proteins could be one of these keys.

Environmental factors in the development of Type 1 diabetes

Environmental factors appear to play an important role in the pathogenesis of childhood-onset type 1 diabetes (T1D). The most important factors are thought to be infectious, dietary, perinatal, and psychosocial. Enteroviruses (especially Coxsackie B virus), breastfeeding, the early presence or lack of certain foods, birth weight, childhood over-nutrition, maternal islet autoimmunity, and negative stress events have been shown to be related to the prevalence of T1D. However, clear conclusions to date are limited because most studies lacked power to detect exposure/disease associations, were not prospective or long-term, did not start in infancy, had imprecise or infrequent exposure estimates, had confounding exposures, and failed to account for genetic susceptibility. In addition to the identification of specific antigenic triggers, several more general hypotheses, including the accelerator and hygiene hypotheses, are testable approaches worth pursuing.

Lower consumption of cow milk protein A1 beta-casein at 2 years of age, rather than consumption among 11- to 14-year-old adolescents, may explain the lower incidence of type 1 diabetes in Iceland than in Scandinavia

AIM

To compare the consumption of the cow milk proteins A1 and B beta-casein among children and adolescents in Iceland and Scandinavia (Norway, Denmark, Sweden and Finland) as this might explain the lower incidence of type 1 diabetes (per 100,000/year, 0-14 years) in Iceland.

METHODS

The consumption of A1 beta-casein in each country among 2- and 11- to 14-year-old children was calculated from results on food intake and on cow milk protein concentration. The consumption values were then compared and evaluated against the incidence of type 1 diabetes.

RESULTS

There was a significant difference between the consumption of A1 (p = 0.034) as well as the sum of A1 and B (p = 0.021) beta-casein in Iceland and Scandinavia for 2-year-old children. In the same age group, consumption of A1 beta-casein correlated with the incidence of type 1 diabetes in the countries (r = 0.9; p = 0.037). No significant difference in consumption of A1 or the sum of A1 and B beta-casein was found for 11- to 14-year-old adolescents.

CONCLUSION

This study supports that lower consumption of A1 beta-casein might be related to the lower incidence of type 1 diabetes in Iceland than in Scandinavia. Additionally it indicates that consumption in young childhood might be of more importance for the development of the disease incidence than consumption in adolescence.

Wheat protein-induced proinflammatory T helper 1 bias in mesenteric lymph nodes of young diabetes-prone rats

AIMS/HYPOTHESIS

Type 1 diabetes is the result of an inflammatory T helper 1 (Th1) lymphocyte-mediated beta cell destructive process. The majority of diabetes-prone BioBreeding (BBdp) rats fed wheat protein-based diets, such as NTP-2000, develop type 1 diabetes and display a mild coeliac-like enteropathy. Mesenteric lymph nodes (MLNs), which drain the gut, are the major inductive site where dietary antigens are recognised in the gut-associated lymphoid tissue (GALT). We hypothesised that this compartment could be a site of abnormal wheat protein-induced Th1 cell activation.

METHODS

MLN cells were isolated from BBdp and BB control (BBc) rats that were fed NTP-2000 or a hydrolysed casein (HC)-based diet at ages that pre-date classic insulitis. The inflammatory status, phenotype and proliferation of these cells in response to wheat protein were determined.

RESULTS

The expression ratio of T-bet : Gata3, master transcription factors for Th1 and Th2 cytokines, was increased in the MLN from NTP-2000-fed BBdp rats compared with that from BBc rats, mainly due to decreased Gata3 expression. CD3(+)CD4(+)IFN-gamma(+) T cells were more prevalent in the MLN of wheat-fed BBdp rats, but remained at control levels in BBdp rats fed a diabetes-retardant HC diet. BBdp MLN cells proliferated in response to wheat protein antigens in a specific, dose-dependent manner, and >93% of cells were CD3(+)CD4(+) T cells. This proliferation was associated with a low proportion of CD4(+)CD25(+) T cells and a high proportion of dendritic cells in the MLN of BBdp rats.

CONCLUSIONS/INTERPRETATION

Before insulitis is established, the MLNs of wheat-fed BBdp rats contain an unusually high proportion of Th1 cells that proliferate specifically in response to wheat protein antigens.

Dietary manipulation of beta cell autoimmunity in infants at increased risk of type 1 diabetes: a pilot study

AIMS/HYPOTHESIS

We aimed to assess the feasibility of a dietary intervention trial with weaning to hydrolysed formula in infants at increased risk of type 1 diabetes and to study the effect of the intervention on the emergence of diabetes-associated autoantibodies in early childhood.

METHODS

We studied 242 newborn infants who had a first-degree relative with type 1 diabetes and carried risk-associated HLA-DQB1 alleles. After exclusive breastfeeding, the infants underwent a double-blind, randomised pilot trial of either casein hydrolysate (Nutramigen; Mead Johnson) or conventional cow's milk-based formula until the age of 6-8 months. During a mean observation period of 4.7 years, autoantibodies to insulin, anti-glutamic acid decarboxylase and insulinoma-associated antigen-2 were measured by radiobinding assays, and islet cell antibodies (ICA) by immunofluorescence.

RESULTS

The feasibility of screening and identifying a cohort of first-degree relatives with HLA-conferred disease susceptibility, enrolling them in a dietary intervention trial and following them for seroconversion to autoantibody positivity is established. The cumulative incidence of autoantibodies was somewhat smaller in the casein hydrolysate vs control formula group, suggesting the need for a larger well-powered study. After adjustment for duration of study formula feeding, life-table analysis showed a significant protection by the intervention from positivity for ICA (p=0.02) and at least one autoantibody (p=0.03).

CONCLUSIONS/INTERPRETATION

The present study provides the first evidence ever in man, despite its limited power, that it may be possible to manipulate spontaneous beta cell autoimmunity by dietary intervention in infancy.

Duration of breast feeding and bovine serum albumin antibody levels in type 1 diabetes: a case-control study

OBJECTIVE

To compare the levels of bovine serum albumin (BSA) antibodies and their relationship with duration of breast feeding, age of exposure to cow's milk, and human leukocyte antigen (HLA-DQ) genotype in children with and without type 1 diabetes.

METHODS

Serum samples from 143 (0.3-14.7 yr) newly diagnosed children with type 1 diabetes and 107 unrelated control children (0.8-13.5 yr) were evaluated for BSA antibodies. Duration of breast feeding and exposure to cow's milk were recorded on questionnaires. HLA-DQ typing was determined by polymerase chain reaction.

RESULTS

One hundred percent of the diabetic children were positive for BSA antibodies compared to 1.9% for healthy controls (p < 0.001). Diabetic children also had higher levels of immunoglobulin G antibodies than unrelated controls (55.1 vs. 17.8 ng/mL, p < 0.0001). Duration of breast feeding (5.4 vs. 7.6 months, p < 0.02), but not age of exposure to cow's milk (8.3 vs. 9.2 months, p = 0.11), differed between cases and controls. There was no difference in antibody titer by duration of breast feeding or age of exposure to cow's milk in the cases or controls.

CONCLUSION

Higher levels of antibodies to BSA were found in children recently diagnosed with type 1 diabetes compared to the controls, particularly those with high or moderate HLA-DQ genotypes. The BSA profile, however, does not seem to depend on duration of breast feeding or age of exposure to cow's milk in this population.

Gliadin, endomysial and thyroid antibodies in patients with latent autoimmune diabetes of adults (LADA)

Latent autoimmune diabetes of adults (LADA) manifested after the age of 35 is characterized by the presence of disease-specific autoantibodies (anti-glutamate decarboxylase GADAb, anti-IA2Ab). However, autoimmunity in Type 1 diabetes mellitus is not targeted only to pancreatic beta-cells. No data have so far been published concerning the antibodies associated with other autoimmune disease in LADA patients. The presence of anti-thyroglobulin (TGAb), anti-thyroid peroxidase (TPOAb), anti-gliadin IgA (AGAAb) and IgG (AGGAb) and endomysial antibodies (EMAb) in sera of 68 diabetics typed as LADA was compared with the antibody presence in sera of 85 patients with Type 2 diabetes. We found a significantly higher occurrence of gliadin antibodies in LADA patients: the rate of AGGAb was 19.1% in comparison with 3.5% in the T2DM group (P = 0.0026), the rate of AGAAb was 13.2% in comparison with 3.5% (P = 0.035). The prevalence of EMAb was very low in both groups (1.5% and 0). The two groups differed significantly in the TPOAb rate: 22.1% in LADA compared to 9.4% in T2DM (P = 0.04), whereas no significant difference was found in the presence of TGAb (8.8% and 3.5%, P = 0.187). In comparison with T2DM patients, LADA patients were found to express higher antibody activity against gluten-related antigens and against TPO.

Short-term dietary adjustment with a hydrolyzed casein-based diet postpones diabetes development in the diabetes-prone BB rat

From earlier studies it appears that weaning associated changes in the animal's physiology and that of the pancreas in particular, render diabetes-prone Bio-Breeding (DP-BB) rats susceptible to the induction and development of insulin-dependent diabetes mellitus (IDDM). In this study we tested whether a short-term dietary adjustment at weaning would influence the development of diabetes later in life. For this purpose a diet in which the protein source was replaced with hydrolyzed casein (HC) was given to the rats from weaning to 60 days of age and from weaning to 130 days of age. The control group received the cereal-based standard diet throughout the experiment. The short-term dietary adjustment resulted in a significant delay of diabetes development. The rats fed the HC diet from weaning to 130 days of age showed a lower incidence of diabetes at 130 days of age. No differences were seen in the histological insulitis scores between the rats of the different treatment groups. Interestingly, when testing (mucosal) immune functions of short-term HC-fed rats, their mesenteric lymph node cells (MLNC) showed increased interferon-gamma (IFN-gamma) and reduced interleukin-10 (IL-10) production after in vitro stimulation. These results demonstrate that short-term dietary adjustments at a young age can influence the course of diabetes later in life. The shift in cytokine profile of MLNC of the HC-fed rats suggests that mechanisms involved can be at the level of both the (mucosal) immune system and the beta cell.

Transcript expression of two Iglambda rearrangements and RAG-1/RAG-2 in a mature human B cell producing IgMlambda islet cell autoantibody

A human B cell clone, EBV-MB91, producing IgMlambda islet cell autoantibody (ICA), obtained by Epstein-Barr virus (EBV) transformation of peripheral CD5- surface Ig+ B cells from a Type 1 diabetic child, and an EBV-MB91-derived hetrohybridoma, HY-MB91, were analyzed for rearranged Ig genes. Both EBV-MB91 and HY-MB91 contained and expressed a unique IgH chain rearrangement (unmutated VH5-51-D6-19-JH5) but contained and expressed two Iglambda chain rearrangements: (i) Vlambda1-4-Jlambda3-Clambda3, which encoded the Iglambda chains (pI, 8.0) of IgMlambda-ICA, showing few mutations but consistent with Ag-driven selection according to the multinomial probability model; and (ii) Vlambda4-1-Jlambda3-Clambda3, with more mutations but inconsistent with antigen-driven selection and involving stop codons that precluded Iglambda synthesis. HY-MB91 showed a progressive loss of IgMlambda-ICA secretion, which was coupled with transcripts of the aberrant Vlambda4-1-Jlambda3-Clambda3 predominating (1.7-fold) over those of Vlambda1-4-Jlambda3-Clambda3. EBV-MB91 also showed the loss of IgMlambda-ICA secretion, associated with cell death. RAG-1 and RAG-2 transcripts occurred in EBV-MB91 but not in HY-MB91, indicating that the former but not the latter might have been able to exhibit V(D)J recombinase activity. Data show that a mature nonmalignant human B cell clone producing IgMlambda-ICA can express RAG-1/RAG-2 transcripts. That the aberrant Vlambda4-1-Jlambda3-Clambda3 was a nonproductive rearrangement occurring at the pre-B cell stage cannot be excluded. However, the hypothetical possibility that one of the two rearrangements corresponded to a secondary rearrangement occurring in the mature B cell represented by the EBV-MB91 clone might also be considered and is discussed.

Environmental factors in the etiology of type 1 diabetes

Type 1 diabetes is considered to be an autoimmune disease in which T lymphocytes infiltrate the islets of pancreas and destroy the insulin producing beta cell population. Besides antigen specificity, the quality of immune reactivity against islet cell antigen(s) is an important determinant of the beta cell destruction. Much evidence indicates that the function of the gut immune system is central in the pathogenesis, as the regulation of the gut immune system may be aberrant in type 1 diabetes. The role of virus infections in the pathogenesis of type 1 diabetes has been supported by substantial new evidence suggesting that one virus group, enteroviruses, may trigger the beta-cell damaging process in a considerable proportion of patients. The latest evidence comes from studies indicating the presence of viral genome in diabetic patients and from prospective studies confirming epidemiological risk effect. If this association holds still true in ongoing large-scale studies, intervention trials should be considered to confirm causality. Of the dietary putative etiological factors, cow's milk proteins have received the main attention. Many studies indicate an association between early exposure to dietary cow's milk proteins and an increased risk of type 1 diabetes. The question will be answered by a large scale, prospective, randomized, international intervention trial. Another dietary factor in need of more studies is the deficiency of vitamin D. Among toxins, N-nitroso compounds are the main candidates. An interaction of genetic and environmental factors is important in evaluating the possible role of a certain environmental factor in the etiology of type 1 diabetes.

Oral exposure to diabetes-promoting food or immunomodulators in neonates alters gut cytokines and diabetes

Disease development in diabetes-prone BB rats is modified by the type of diet fed after weaning. The aim of this investigation was to determine whether exposure during the first week of life to antigens from a known diabetes-promoting diet (NIH-07) could modify diabetes incidence and, if so, to what extent this occurs via alterations in systemic T-cell reactivity, gut cytokines, or islet infiltration. Diabetes-prone BB (BBdp) rats were hand-fed twice daily between age 4 and 7 days with vehicle, a hydrolyzed casein (HC)-based infant formula, Pregestimil (PG), PG + cereal-based NIH-07 diet, PG + lipopolysaccharides (LPS) or PG + LPS + silica. After weaning, they were fed either an NIH-07 diet or a semipurified HC (diabetes-retardant) diet until 150 days. In separate studies, 5-day-old BBdp rat pups were administered the aforementioned treatments, and expression of intestinal mRNA for gamma-interferon (IFN-gamma) or transforming growth factor-beta (TGF-beta) was quantified using reverse transcriptase-polymerase chain reaction. The effect of early oral treatment with NIH-07 or PG on systemic T-cell reactivity was evaluated using footpad swelling delayed-type hypersensitivity (DTH) and the popliteal lymph node assay. Oral exposure of neonates to a complex mixture of antigens from the diabetes-promoting diet delayed onset of diabetes (79 vs. 88 days) and prevented disease in approximately one-third of animals. A similar protective effect was seen for neonatal exposure to wheat gluten in animals subsequently weaned onto a semipurified wheat gluten diet. By contrast, LPS-treated neonates displayed more severe insulitis and developed diabetes at an increased rate, which was significantly suppressed by co-administration of silica particles. The protective effect of early exposure to diabetogenic diets was not associated with significant reduction of islet infiltration, and there was no impact on the DTH response to food antigens. However, whereas diabetes-resistant BBc rats developed systemic tolerance to NIH-07 antigens fed chronically, BBdp rats did not. The lack of effect of the early oral antigen regimen on the DTH reaction in the footpad, a classic Th1-mediated reaction, suggests little effect on systemic T-cell reactivity. However, local effects were observed in the small intestine. Oral exposure to diabetes-promoting food antigens or LPS downregulated the Th1 cytokine IFN-gamma and decreased the IFN-gamma/TGF-beta ratio. Thus, oral exposure to diabetes-promoting food antigens and immune modulators in neonates can modify diabetes expression in association with changes in local cytokine balance in the gut.

Dietary fatty acid modulation of mucosally-induced tolerogenic immune responses

Immunological unresponsiveness or hyporesponsiveness (tolerance) can be induced by feeding protein antigens to naive animals. Using a classical oral ovalbumin gut-induced tolerance protocol in BALB/c mice we investigated the effects of dietary n-6 and n-3 polyunsaturated fatty acids (PUFA) on high-and low-dose oral tolerance (and in non-tolerised animals, i.e. effects of antigen challenge alone) in relation to lymphoproliferative, cytokine and antibody responses. Fish oil rich in long-chain n-3 fatty acids decreased both T-helper (Th) 1- and Th2-like responses. In contrast, borage (Borago officinalis) oil rich in n-6 PUFA, of which gamma-linolenic acid is rapidly metabolised to longer-chain n-6 PUFA, increased Thl-like responses and decreased Th2-like responses, and possibly enhanced suppressor cell or Th3-like activity. These findings are in general agreement with other studies on the effects of long chain n-3 PUFA on immune system functions, and characterise important differences between long-chain n-3 and n-6 PUFA, defining more precisely and broadly the immunological regulatory mechanisms involved. They are also discussed in relation to autoimmune disease.

Nutrition and the mucosal immune system

Gut-associated lymphoid tissue is the dominant site for the initiation of mucosal immune response. Mucosal immunity depends on regulatory signals; nutritional elements, including fats, amino acids, and micronutrients, are critical cofactors for these signals. Nutrients specifically affect lymphocyte influx and migration, mononuclear cell activation, and the differentiated expression of immune response. The molecular basis of nutrient action has been shown to involve effects on receptor regulation, adhesion molecule expression, and the pattern of cytokine production. The gastrointestinal mucosal immune system is the major site for host interaction with microbes and provides a barrier against systemic access for food antigens and microbes. Nutrient metabolism has unique and direct impact on the host defense system of gut-associated lymphoid tissue and therefore has potential for widely disseminated impact on systemic immune response.

Bovine beta-casein antibodies in breast- and bottle-fed infants: their relevance in Type 1 diabetes

BACKGROUND

Bovine beta-casein is a cow's milk protein that targets both humoral and cellular immune responses in patients with Type 1 diabetes and, to a lesser degree, also in normal subjects. In this study we aimed to determine whether the avoidance of cow's milk consumption early in life could prevent the development of antibody response to bovine beta-casein despite the mother being exposed on a daily basis to cow's milk consumption.

MATERIALS AND METHODS

We measured the antibody response to bovine beta-casein using an ELISA method in 28 healthy infants under 4 months of age, of whom 16 were exclusively breast-fed and 12 were bottle-fed with cow's milk. In addition, beta-casein antibodies were measured in 37 prepubertal children with Type 1 diabetes and in 31 healthy children who were exposed to cow's milk or dairy products to see whether differences in antibody titers exist in this young age group. Antibodies binding to beta-casein were also evaluated by immunoblotting analysis.

RESULTS

Elevated levels of beta-casein antibodies were found in bottle-fed infants compared to breast-fed infants (p<0.0001). Antibody levels to bovine beta-casein were also significantly higher in children with Type 1 diabetes compared to age-matched controls (p=0.03). By western blot analysis we confirmed specific binding to bovine beta-casein in bottle-fed infants, in children with Type 1 diabetes and in controls exposed to cow's milk, but not in infants who were exclusively breast-fed.

CONCLUSIONS

The results of this study indicate that breastfeeding within the first 4 months of life prevents the generation of antibody response to bovine beta-casein despite the mothers' consumption of cow's milk during the breastfeeding period. These findings may have relevance for disease prevention.

Cow's milk and immune-mediated diabetes

Cow's milk-based infant formulas and cow's milk consumption in childhood have been suggested to promote the development of type 1 diabetes mellitus and other immune-mediated or neurological diseases. Epidemiological studies in man have led to the hypothesis that introduction of cow's milk-based infant formula within the first 3 months of life is associated with increased risk of type 1 diabetes mellitus. Furthermore, in animal models of type 1 diabetes mellitus, cow's milk proteins have been proven to be 'diabetogenic'. However, the issue seems far from being resolved. Several epidemiological studies and, more importantly, the first prospective trials did not show an association between early exposure to cow's milk and type 1 diabetes mellitus. In animal models, cow's milk proteins are modestly and variably diabetogenic, wheat or soybean proteins in the diet cause higher rates of autoimmune diabetes. In both man and rodents there is increasing evidence that the gut-associated immune system plays a major role in disease development, probably because of disturbed oral tolerance mechanisms. Oral tolerance depends on immunological homeostasis and normal maturation of the gut. These factors are influenced by growth factors and cytokines from breast milk, normal bacterial colonization, infections and diet. All these factors have been proposed as risk factors for type 1 diabetes mellitus. Hence, cow's milk proteins may provide mimicry epitopes relevant in autoimmunity, as well as destabilizing oral tolerance mechanisms by biologically active peptides. The concept of dietary regulation of autoimmunity does not apply only to cow's milk protein, but also to other dietary proteins.

Early nutrition and the development of immune function in the neonate

The present review will concentrate on the development of the gut-associated lymphoid tissue and the role of early nutrition in promoting immune function. The intestine is the largest immune organ in the body, and as such is the location for the majority of lymphocytes and other immune effector cells. The intestine is exposed to vast quantities of dietary and microbial antigens, and is the most common portal of entry for pathogens, some of which are potentially lethal. The development of normal immune function of the intestine is therefore vital for survival, and is dependent on appropriate antigen exposure and processing, and also an intact intestinal barrier. In early life innate mechanisms of defence are probably more important than active or adaptive mechanisms in responding to an infectious challenge, since the healthy neonate is immunologically naïve (has not seen antigen) and has not acquired immunological memory. During this period maternal colostrum and milk can significantly augment resistance to enteric infections. The mechanisms of enhancing disease resistance are thought to be passive, involving a direct supply of anti-microbial factors, and active, by promoting the development of specific immune function. A tolerance response to dietary and non-invasive antigens is generally induced in the gut. However, it must also be able to mount an adequate immune response to ensure clearance of foreign antigens. It is now recognized that regulation of tolerance and active immune responses is critical to health, and failure to regulate these responses can lead to recurrent infections, inflammatory diseases and allergies. The education of the immune system in early life is thought to be critical in minimizing the occurrence of these immune-based disorders. During this phase of development maternal milk provides signals to the immune system that generate appropriate response and memory. One factor that has been proposed to contribute to the increase in the incidence of immune-based disorders, e.g. atopic diseases in Western countries, is thought to be the increased prevalence of formula-feeding.