The case for elimination of cow's milk in early infancy in the prevention of type 1 diabetes: the Finnish experience

Combination immunotherapies for type 1 diabetes mellitus

Immunotherapies for type 1 diabetes mellitus (T1DM) have been the focus of intense basic and clinical research over the past few decades. Restoring β-cell function is the ultimate goal of intervention trials that target the immune system in T1DM. In an attempt to achieve this aim, different combination therapies have been proposed over the past few years that are based on treatments tackling the various mechanisms involved in the destruction of β cells. The results of clinical trials have not matched expectations based on the positive results from preclinical studies. The heterogeneity of T1DM might explain the negative results obtained, but previous trials have not addressed this issue. However, novel promising combination therapies are being developed, including those that couple immunomodulators with drugs that stimulate β-cell regeneration in order to restore normoglycaemia. This strategy is an encouraging one to pursue the goal of finding a cure for T1DM. This Review summarizes the available data about combination immunotherapies in T1DM, particularly addressing their clinical importance. The available data supporting the use of registered drugs, such as proton pump inhibitors and incretin-based agents, that have been shown to induce β-cell regeneration will also be discussed.

Risk factors and primary prevention trials for type 1 diabetes

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease resulting in the designated immune destruction of insulin producing β-cells, usually diagnosed in youth, and associated with important psychological, familial, and social disorders. Once diagnosed, patients need lifelong insulin treatment and will experience multiple disease-associated complications. There is no cure for T1DM currently. The last decade has witnessed great progress in elucidating the causes and treatment of the disease based on numerous researches both in rodent models of spontaneous diabetes and in humans. This article summarises our current understanding of the pathogenesis of T1DM, the roles of the immune system, genes, environment and other factors in the continuing and rapid increase in T1DM incidence at younger ages in humans. In addition, we discuss the strategies for primary and secondary prevention trials of T1DM. The purpose of this review is to provide an overview of this disorder's pathogenesis, risk factors that cause the disease, as well as to bring forward an ideal approach to prevent and cure the disorder.

Primary and secondary prevention of Type 1 diabetes

Since type 1 diabetes is an immunologically mediated disease, immune intervention should alter the natural history of the disease. This article reviews prevention studies undertaken either prior to any evidence of autoimmunity (primary prevention) or after the development of islet autoantibodies (secondary prevention). Most immune intervention studies have been conducted in recent-onset type 1 diabetes (tertiary prevention), and these are not reviewed herein. The goal of primary and secondary intervention is to arrest the immune process and thus prevent or delay clinical disease. Primary prevention studies have been conducted in infants with high genetic risk. Interventions tested include several dietary manipulations, including infant formulas free of either cow's milk or of bovine insulin, infant formula supplemented with the omega-3-fatty acid docosahexaenoic acid, delayed introduction of gluten-containing foods, and vitamin D supplementation. Secondary prevention studies have been conducted in both children and adults with diabetes autoantibodies. Interventions tested include nicotinamide, insulin injections, oral insulin, nasal insulin, glutamic acid decarboxylase, and cyclosporine. Underway are secondary prevention studies with teplizumab and with abatacept.

Transfer of maternal immunity to newborns of diabetic mothers

This study was carried out with hyperglycemic pregnant women to investigate the transfer of antibody classes to newborns across the placenta or by colostrum and the functional activity of phagocytes in maternal blood, cord blood, and colostrum from diabetes mothers. Samples from maternal blood, cord blood, and colostrum were collected from 20 normoglycemic and 20 hyperglycemic pregnant women. We determined antibodies levels, superoxide release, phagocytosis and bactericidal activity of phagocytes. We demonstrated that IgG levels in cord blood were higher in the hyperglycemic group. IgA and IgM levels were higher in maternal than in cord blood samples. Plasma antibody levels were lower in hyper- than in normoglycemic women. The colostrum of diabetic mothers had lower IgA and IgG levels. Colostrum and maternal blood phagocytes when exposed to EPEC increased the superoxide release. Cord blood phagocytes of hyperglycemic group, independently of bacteria, had higher superoxide release. Colostrum and blood phagocytes from diabetic group exhibited some phagocytic and microbicidal activity in response to EPEC. Mononuclear phagocytes from cord blood had the lowest phagocytosis, and bactericidal activity for EPEC, regardless of glycemic status. These data showed that hyperglycemia altered IgG transfer across the placenta and decreases immunoglobulin levels in maternal blood and colostrum.

The pancreas in human type 1 diabetes

Type 1 diabetes (T1D) is considered a disorder whose pathogenesis is autoimmune in origin, a notion drawn in large part from studies of human pancreata performed as far back as the 1960s. While studies of the genetics, epidemiology, and peripheral immunity in T1D have been subject to widespread analysis over the ensuing decades, efforts to understand the disorder through analysis of human pancreata have been far more limited. We have reviewed the published literature pertaining to the pathology of the human pancreas throughout all stages in the natural history of T1D. This effort uncovered a series of findings that challenge many dogmas ascribed to T1D and revealed data suggesting the marked heterogeneity in terms of its pathology. An improved understanding and appreciation for pancreatic pathology in T1D could lead to improved disease classification, an understanding of why the disorder occurs, and better therapies for disease prevention and management.

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.

Genetics and type 1 diabetes: online resources for diabetes educators

PURPOSE

Genetic education Internet sites and peer-reviewed medical literature were reviewed and critiqued to develop tables summarizing online resources for diabetes health professionals.

METHODS

Using Internet search engines, each Web site identified for this project met the following criteria: (1) accurate and valid site content based on widely accepted genetic texts, (2) credibility of the organization that maintained the Web site, (3) ease of navigation, and (4) provision of continuing education credits. PubMed was used to find journal articles using similar criteria.

RESULTS

There were 33 Web sites on genetic education for diabetes health professionals that met the inclusion criteria. The literature search identified 36 articles regarding the importance of genetic education for nurses and other health professionals, as well as information regarding genetics and diabetes.

CONCLUSIONS

Valid and credible information on genetics and type 1 diabetes is available for diabetes health professionals on the Internet and in the medical literature.

Estudo caso-controle sobre exposição precoce ao leite de vaca e ocorrência de Diabetes Mellitus tipo 1 em Campina Grande, Paraíba

OBJETIVOS: estudar a relação entre exposição precoce ao leite de vaca e ocorrência de Diabetes Mellitus tipo 1 entre menores de 18 anos atendidos no Hospital Universitário Alcides Carneiro, em Campina Grande. MÉTODOS: estudo caso-controle. A amostra foi constituída por 128 indivíduos de ambos os sexos. Foram entrevistadas 64 mães de portadores de Diabetes Mellitus e 64 mães de controles. Análises univariadas e multivariadas foram utilizadas. RESULTADOS: 84,4% dos indivíduos diabéticos foram expostos ao leite de vaca antes dos quatro meses de idade, enquanto que no grupo controle este percentual foi de 64,1%. A análise univariada identificou uma associação estatisticamente significante entre exposição precoce ao leite de vaca e Diabetes (p = 0,01). Na análise multivariada, essa associação permaneceu e a razão chances estimada foi de 4,09 (IC95%: 1,19 - 14,04; p = 0,01). CONCLUSÕES: os resultados indicam uma forte associação entre exposição precoce ao leite de vaca e ocorrência de Diabetes Mellitus tipo1 na população estudada. Assim, crianças expostas precocemente ao leite de vaca apresentam uma chance maior de adquirir a doença quando comparadas àquelas que receberam aleitamento materno exclusivo até pelo menos quatro meses após o nascimento.

Prediabetes in children: natural history, diagnosis, and preventive strategies

The clinical manifestation of type 1 diabetes mellitus is preceded by an asymptomatic prodromal period called prediabetes or preclinical diabetes. It may last from a few months to several years, during which the autoimmune destruction of the insulin-producing beta-cells in the pancreas progresses. The genes on the human leukocyte antigen (HLA) and insulin gene region are major genetic determinants for genetic disease susceptibility, while dietary compounds and viral infections are the most likely environmental factors contributing to the etiopathogenesis. T cells are thought to be the effector cells for the beta-cell destruction, and glutamic acid decarboxylase, insulinoma-associated protein 2 and insulin represent the three major autoantigens. Autoantibodies are early detectable markers of an ongoing disease process and are used to diagnose prediabetes. Among first-degree relatives of patients with type 1 diabetes, the risk for clinical disease can be graded from <5% in those with one or no antibodies to >90% in individuals who carry the HLA-DQB1*02/0302 risk genotype and are positive for multiple autoantibodies. beta-Cell function may also be tested in autoantibody-positive individuals and low first-phase insulin response is highly predictive for rapid progression to the clinical disease. However, dynamic course and individual variation of the disease process complicates the disease prediction, and it is not known whether all individuals with signs of prediabetes will inevitably progress to clinical type 1 diabetes. Until clinically applicable prevention for the condition exists, the screening for the risk markers of type 1 diabetes should actively be undertaken only in the context of research projects. Several major national and international multicenter studies are ongoing to test the potential of various agents (e.g. insulin and nicotinamide) or early elimination of dietary compounds (e.g. cow's milk proteins) to delay or prevent the onset of clinical type 1 diabetes.

Enterovirus infections as a risk factor for type I diabetes: virus analyses in a dietary intervention trial

This study evaluated the possible role of enterovirus infections in the pathogenesis of type I (insulin-dependent) diabetes in a prospective dietary intervention trial. Children participated in the second pilot of the Trial to Reduce IDDM in Genetically at Risk (TRIGR) project. They were randomized into two groups receiving either a casein hydrolysed formula (Nutramigen) or a regular formula, whenever breast milk was not available over the first 6-8 months of life. Altogether 19 children who turned positive for autoantibodies associated with type I diabetes by 2 years of age and 84 matched control children were analysed for enterovirus antibodies and enterovirus RNA in serum. Enterovirus infections were common during the first 2 years of life and more frequent among boys than girls (P = 0.02). Autoantibody-positive children had more enterovirus infections than autoantibody-negative children before the appearance of autoantibodies (0.83 versus 0.29 infection per child, P = 0.01). The average levels of IgG antibodies to echovirus antigen were also higher in autoantibody-positive than in autoantibody-negative children (P = 0.0009). No difference was found in the frequency of enterovirus infections between children receiving the casein hydrolysed formula or regular formula. These results suggest that enterovirus infections are associated with the induction of beta-cell autoimmunity in young children with increased genetic susceptibility to type I diabetes.

Prospective assessment in newborns of diabetes autoimmunity (PANDA): maternal understanding of infant diabetes risk

PURPOSE

To assess accuracy of mothers' understanding of their newborns' genetic risk for type 1 diabetes and to identify predictors of the comprehension and retention of genetic information.

METHODS

Mothers of 435 newborns genetically screened at birth were informed of the infant's risk for type 1 diabetes using a standard script that provided both categorical and numerical risk information. The mothers' comprehension and retention of this information were assessed by structured interview on two occasions, approximately 3.6 weeks and approximately 3.9 months postnotification.

RESULTS

At the initial interview, 73.1% of mothers gave a correct estimate of their child's genetic risk, 3.2% overestimated risk, 13.3% underestimated risk, and 10.3% could not recall risk at all. At the follow-up interview, fewer mothers (61.9%) correctly estimated their child's risk and more mothers (24.4%) underestimated their child's risk. Maternal accuracy was associated with maternal education, ethnic minority status, infant risk status, maternal ability to spontaneously recall both categorical and numerical risk estimates, and length of time since risk notification. Underestimation of risk was associated with maternal education, family history of diabetes, time since risk notification, and maternal anxiety about the baby's risk.

CONCLUSION

The accuracy of mothers' recall of infant risk declines over time, with an increasing number of mothers underestimating the infant's risk. Effective risk communication strategies need to be developed and incorporated into genetic screening programs.

Disease-associated autoantibodies during pregnancy and at birth in families affected by type 1 diabetes

We studied the pattern of type 1 diabetes-associated autoantibodies during pregnancy and the transplacental transfer of these autoantibodies to the fetal circulation and searched for possible signs of prenatal induction of beta-cell autoimmunity in newborn infants. The population comprised 208 mothers and their newborn infants. Seventy-four of the mothers (36%) had type 1 diabetes and 134 (64%) of the infants had an affected father or sibling. Blood samples were obtained from the mother at the end of the first trimester and at delivery, and from the cord blood of the newborn infant. Close to 40% of the mothers with type 1 diabetes had antibodies to islet cells (ICA), 55% to glutamic acid decarboxylase (GADA) and 54% to the IA-2 protein (IA-2A) in early pregnancy, whereas the corresponding frequencies in the nonaffected mothers were 5.2%, 5.2% and 3.0%. No significant changes could be seen in autoantibody levels during pregnancy, and there was a close correlation between the two maternal samples. One third of the infants of mothers with type 1 diabetes tested positive for ICA, 50% for GADA and 51% for IA-2A. Six percent of the infants of nondiabetic mothers had ICA, 2.2% GADA and none had IA-2A. None of the infants of the antibody negative mothers had antibodies in their cord blood. These observations indicate that the immunomodulatory effect of pregnancy on signs of beta-cell autoimmunity is weak, but if diabetes-associated autoantibodies are present in the mother, most of them are transferred to the fetal circulation. Our data do not provide any support for fetal induction of beta-cell autoimmunity.

Pregnancy induces nonimmunoglobulin insulin-binding activity in both maternal and cord blood serum

To evaluate whether pregnancy has any effect on insulin antibody levels and to test the concordance between a conventional radioimmunoassay and a new microassay for the detection of insulin antibodies, insulin antibodies were analysed in 104 mothers in early pregnancy and at delivery and in their newborn infants. Thirty-eight of the mothers had type 1 diabetes. The concordance between the assays was high in the samples taken in early pregnancy (95%), but substantially lower in the samples taken at delivery (40%) and in the cord blood samples (68%). A considerable proportion of the mothers at delivery, especially the unaffected mothers (71%), and the newborn infants of the unaffected mothers (32%) were positive for insulin antibodies in the conventional assay but not in the microassay. Insulin antibody levels increased in the mothers, significantly so in the unaffected mothers (P < 0.001), during pregnancy in the conventional assay, whereas in the microassay they decreased significantly (P < 0.01) in affected mothers and remained negative in the unaffected mothers. Since immune complexes are precipitated with protein A specific for IgG in the microassay and with polyethylene glycol lacking specificity for immunoglobulins in the conventional assay, our data indicate that insulin antibody levels decrease on average during pregnancy and that the increasing non-IgG anti-insulin activity observed in the conventional assay is induced by pregnancy and is present in both the maternal and the foetal circulation.

Oral administration of insulin to neonates suppresses spontaneous and cyclophosphamide induced diabetes in the NOD mouse

Oral administration of autoantigens to adult mice is an effective means of suppressing experimental autoimmune diseases including diabetes and experimental allergic encephalomyelitis (EAE). Different mechanisms are involved in induction of oral tolerance including active suppression, anergy and deletion. Oral tolerance is generally not inducible in the neonatal period and we previously found that EAE development in Lewis rats is enhanced when animals are fed myelin antigens as neonates. Here we report the unexpected finding that oral administration of either human insulin or the insulin B-chain peptide (10-24) in the neonatal period suppresses the development of diabetes in the non-obese diabetic (NOD) mouse. Furthermore, suppression of diabetes by neonatal oral human insulin was more effective than oral human insulin given to NOD mice (3-4 weeks of age). No protection against EAE was observed in NOD mice neonatally fed PLP (48-70) or MOG (35-55) peptide prior to EAE induction, whereas adult NOD mice orally tolerized to these peptides were protected against EAE. Neonatal administration of insulin B-chain peptide also suppressed cyclophosphamide induced diabetes in the NOD whereas oral insulin administration to 4-week-old NOD mice had no effect, suggesting that the mechanism of disease suppression in the neonate involved anergy or deletion. Our findings that neonatal feeding of human insulin or insulin B-chain peptide is effective in inhibiting diabetes when given to the NOD mouse may have applications in preventing diabetes in high risk human populations.

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

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

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.

Prediction and prevention of type 1 diabetes

Clinical type 1 diabetes represents end-stage insulitis resulting from progressive beta-cell destruction over an asymptomatic period that may last for years. This knowledge and recent advances in our ability to identify individuals at increased risk for clinical disease have paved the way for trials aimed at preventing or delaying the clinical onset of type 1 diabetes. Individuals at risk for type 1 diabetes can be identified by a positive family history, or by genetic, immunological or metabolic markers. These markers can also be combined to achieve a higher positive predictive value. As long as there is no effective preventive modality available for clinical use, screening for the identification of risk individuals can be considered ethically acceptable only in the context of sound research protocols. Prevention of type 1 diabetes can be implemented at three different levels, out of which primary prevention includes all strategies aimed at decreasing the risk of developing type 1 diabetes in individuals without any signs of beta-cell damage. Secondary prevention aims to reduce the incidence of type 1 diabetes by stopping beta-cell destruction in individuals with signs of such a process, while the objective of tertiary prevention is to restore beta-cell function or prevent complications in patients with overt type 1 diabetes. At present, one primary prevention trial and four comprehensive secondary prevention trials are in progress. Common features of these intervention trials are that the recruitment of patients fulfilling the inclusion criteria is time-consuming and the trials must proceed for a long time, as clinical disease is the end point. The secondary prevention trials also require extensive screening for the identification of eligible patients. The ongoing intervention trials may, however, represent a new era in type 1 diabetes, i.e. the beginning of the end of this complicated disease.

Amamentação ao seio, amamentação com leite de vaca e o diabetes mellitus tipo 1: examinando as evidências

A etiologia do diabetes mellitus tipo 1 (DM1) envolve tanto herança genética como a exposição a fatores ambientais. Evidências de estudos epidemiológicos e experimentais sugerem que a dieta pode ser importante na etiopatogenia dessa doença. Em 1984, Borch-Johnsen e col. sugeriram, com base nos resultados de um estudo caso-controle, que o leite materno seria um fator de proteção para o DM1; esse efeito se daria devido às propriedades anti-infecciosas desse tipo de leite, ou pelo fato de que a amamentação ao seio evitaria que as crianças pudessem ser precocemente expostas a outros agentes etiológicos contidos nos substitutos do leite materno. Esses mesmos achados foram poste-riormente encontrados em diversos estudos, mas o papel do leite materno no aparecimento do DM1 ainda permanece controverso. Em 1992, Karjalainen e col., ao compararem os soros de indivíduos com e sem DM1, observaram, entre os diabéticos, altas concentrações de anticorpos anti-albumina bovina. Os autores postularam a hipótese de que a albumina bovina poderia atuar como desencadeadora do processo destrutivo das células ß do pâncreas e, conseqüentemente, do diabetes. Resultados conflitantes foram observados nas publicações que se sucederam a essa. Neste artigo, resumem-se e discutem-se os achados de diferentes pesquisadores que investigaram a importância desses fatores dietéticos para o aparecimento do DM1.

Cow milk feeding induces antibodies to insulin in children--a link between cow milk and insulin-dependent diabetes mellitus?

Exposure to cow milk (CM)-based formulas in early infancy has been associated with an increased risk of insulin-dependent diabetes mellitus (IDDM), but studies on the possible pathogenic mechanism(s) linking CM and IDDM are contradicting. We hypothesized that if CM formulas contained bovine insulin (BI), exposure to them could lead to immunization against insulin, which is the only known beta-cell-specific autoantigen in IDDM. We measured immunoglobulin G (IgG) antibodies by enzyme immunoassay (EIA) to BI and human insulin (HI) in children who received, during the first 9 months of life, either a formula containing whole CM proteins or a formula containing hydrolyzed casein (HC) peptides. BI was detectable by radioimmunoassay (RIA) and immunoblotting in the CM-based formula. At 6 months of age the children who received CM formula had higher levels of IgG antibodies to BI than children who received either HC formula or children who were exclusively breast-fed (median levels 0.480 versus 0.185, P = 0.04; and 0.480 versus 0.160, P = 0.04; respectively). Also, at 9 months of age, children in the CM group differed from the HC group (0.403 versus 0.230; P = 0.02). Antibodies to BI and HI showed a positive correlation and cross-reacted in inhibition studies. The high incidence of insulin-binding antibodies in young children with IDDM may be explained by oral immunization to BI present in CM. Exposure to BI, which differs from HI only by three amino acids, may break the tolerance to insulin.

From pathomechanisms to prediction, prevention and improved care of insulin-dependent diabetes mellitus in children

Molecular biology, gene technology and immunology have extensively clarified the aetiology and pathogenesis of insulin-dependent diabetes mellitus (IDDM). It is now obvious that the genetic background of the individual, poorly characterized environmental factors and aggressive autoimmune phenomena in a complex interplay contribute to the progression to clinical IDDM. The IDDM risk associated with certain genetic markers, e.g. the risk alleles at various HLA loci, the most strongly predisposing gene region, and the mechanisms that mediate the genetic impact may differ in different populations. In Finland the accumulated genetic evidence is so convincing that two IDDM prevention studies have been initiated. One is a population-based prediction and prevention study, while the other is conducted in first-degree relatives of IDDM patients. Both studies rely on screening of newborn infants for IDDM susceptibility alleles at the HLA-DQB1 locus. Meanwhile, in the clinical care of children with IDDM, the importance of intensified and individualized insulin therapy in prevention of diabetic microangiopathy has become increasingly clear, and should be implemented in the care of most paediatric patients.

Genetics in the prediction of insulin-dependent diabetes mellitus: from theory to practice

Only weak associations have been found for particular environmental factors and development of insulin-dependent diabetes mellitus (IDDM). Very few studies have, however, accounted for genetic susceptibility when cases and controls have been compared. The genetics of IDDM is complex, but the HLA-DQ genes are the most important. There are many different combinations of DQA1 and DQB1 genes conferring disease risk to differing degrees. The strategy of NOBADIA (Norwegian Babies against Diabetes) is to identify at birth the babies in the general population with the highest genetic risk for developing IDDM: those carrying DQA1*0301-DQB1*0302/DQA1*0501-DQB1*0201 (for simplification, hereafter named DQ2/DQ8). Four per cent of Norwegian babies carry this genotype which accounts for 46% of future cases of IDDM. Babies carrying the IDDM high-risk genotype have a lifetime risk of 12% for developing the disease. This is very close to the risk of a first-degree relative with the same genotype. DQ2/DQ8 heterozygotes also acquire the disease earlier than those with a lower genetic risk. Parents of children carrying the DQ2/DQ8 genotype will be informed and offered regular follow-up with blood samples and questionnaires at their public health care centre.

Tactics for type I diabetes

This article discusses the evolution of therapy for type I diabetes and considers how physicians should be thinking about the disease in the late 1990s. The biases herein are that management strategy has evolved such that contemporary practice should routinely entail a system of "flexible intensive therapy" directed at meticulous glycemic control. To accomplish this requires a skilled management team including an educated, motivated patient and family working in a negotiated therapeutic alliance; a further goal should be the development of effective approaches to interdict the pathogenetic process such that disease prevention is possible.

Relation between antibodies to islet cell antigens, other autoantigens and cow's milk proteins in diabetic children and unaffected siblings at the clinical manifestation of IDDM. The Childhood Diabetes in Finland Study Group

The relation between islet cell specific antibodies, other autoantibodies and antibodies to cow's milk proteins was studied in IDDM and pre-IDDM by analysing islet cell antibodies (ICA), insulin autoantibodies (IAA), anti-nuclear (ANA), anti-reticulin class IgA [ARA(IgA)], smooth muscle, anti-mitochondria, parietal cell (PCA), adrenal and thyroid antibodies and antibodies to cow's milk formula (CMF), beta-lactoglobulin (BLG) and bovine serum albumin (BSA) in a population based study with more than 650 children with newly diagnosed IDDM and more than 550 initially non-diabetic siblings. After adjustment for age a weak association was seen in the diabetic children between IAA and ANA but none between ICA and autoantibodies directed against the other organ-specific or non-organ-specific antigens. There was no significant difference in cow's milk antibodies between diabetic children with and without ICA or IAA. The siblings with ICA had higher CMF (IgA and IgM) antibody levels and BLG (IgA) antibody levels than the remaining siblings, but no such differences were found when comparing IAA-positive and negative siblings. Siblings positive for ICA had PCA more often than did the ICA-negative siblings, whereas siblings positive for both ICA and PCA had increased levels of antibodies against CMF, BLG and BSA. These findings indicate that the humoral islet cell-associated autoimmunity characteristic of recent-onset childhood IDDM is clearly restricted to the islet cells and not directly related to signs of other organ-specific or non-organ-specific autoimmunity. The observation of increased levels of antibodies to cow's milk proteins in siblings positive for ICA suggests that the immune response to cow's milk proteins may be related to the progressive autoimmune process resulting in beta-cell destruction and ultimately in the clinical manifestation of IDDM. Gastrointestinal autoimmune mechanisms may play a role in the pathogenesis of IDDM, and the association observed between combined ICA and PCA positivity and increased levels of antibodies to cow's milk proteins in the siblings implies that there may be an enhanced transfer of nutritional antigens across the gut barrier in these subjects.

Dietary factors in the aetiology of diabetes

Quite different nutrition-related environmental factors influence the development of type 1 insulin-dependent diabetes (IDDM) and type 2 non-insulin-dependent diabetes (NIDDM). IDDM is characterized by progressive beta-cell destruction which leads to complete insulin deficiency; at the time of diagnosis 80-90% of beta cells have been destroyed. In children there is epidemiological evidence that high intake of nitrites and N-nitroso compounds, early introduction of cow's milk to the diet and short duration or absence of breastfeeding increase the risk of IDDM. Studies in experimental animals suggest that cow's milk and soy proteins may be diabetogenic. There is current interest in the effects of free radical scavengers, particularly niacin and natural and synthetic antioxidants on the incidence of IDDM. These findings from ecological, animal, and human case-control studies remain to be evaluated in prospective cohort studies covering infancy and childhood and finally in human intervention trials. NIDDM is characterized by insulin resistance which is complicated by impaired insulin secretion at the time of appearance of hyperglycaemia and clinical diabetes. Its preclinical development is insidious and poorly defined, and there is little direct evidence that the same factors which influence metabolic control in clinical diabetes also affect the preclinical development of the disorder. Obesity, particularly of the abdominal type, is common in people who develop NIDDM, and weight control by appropriate diet and physical activity is probably the most important measure for preventing NIDDM. High (saturated) fat intake seems to be associated with insulin resistance, obesity and increased risk of NIDDM, and diets high in carbohydrate seem to protect from glucose intolerance and diabetes, mainly owing to their high fibre content.