Primary prevention of beta-cell autoimmunity and type 1 diabetes - The Global Platform for the Prevention of Autoimmune Diabetes (GPPAD) perspectives.

OBJECTIVE: Type 1 diabetes can be identified by the presence of beta-cell autoantibodies that often arise in the first few years of life. The purpose of this perspective is to present the case for primary prevention of beta-cell autoimmunity and to provide a study design for its implementation in Europe. METHODS: We examined and summarized recruitment strategies, enrollment rates, and outcomes in published TRIGR, FINDIA and BABYDIET primary prevention trials, and the TEDDY intensive observational study. A proposal for a recruitment and implementation strategy to perform a phase II/III primary prevention randomized controlled trial in infants with genetic risk for developing beta-cell autoimmunity is outlined. RESULTS: Infants with a family history of type 1 diabetes (TRIGR, BABYDIET, TEDDY) and infants younger than age 3 months from the general population (FINDIA, TEDDY) were enrolled into these studies. All studies used HLA genotyping as part of their eligibility criteria. Predicted beta-cell autoimmunity risk in the eligible infants ranged from 3% (FINDIA, TEDDY general population) up to 12% (TRIGR, BABYDIET). Amongst eligible infants, participation was between 38% (TEDDY general population) and 97% (FINDIA). Outcomes, defined as multiple beta-cell autoantibodies, were consistent with predicted risks. We subsequently modeled recruitment into a randomized controlled trial (RCT) that could assess the efficacy of oral insulin treatment as adapted from the Pre-POINT pilot trial. The RCT would recruit infants with and without a first-degree family history of type 1 diabetes and be based on general population genetic risk testing. HLA genotyping and, for the general population, genotyping at additional type 1 diabetes susceptibility SNPs would be used to identify children with around 10% risk of beta-cell autoimmunity. The proposed RCT would have 80% power to detect a 50% reduction in multiple beta-cell autoantibodies by age 4 years at a two-tailed alpha of 0.05, and would randomize around 1160 infants to oral insulin or placebo arms in order to fulfill this. It is estimated that recruitment would require testing of between 400,000 and 500,000 newborns or infants. CONCLUSION: It is timely and feasible to establish a platform for primary prevention trials for type 1 diabetes in Europe. This multi-site European infrastructure would perform RCTs, supply data coordination and biorepository, provide cohorts for mechanistic and observational studies, and increase awareness for autoimmune diabetes.

Compromised immune response in infants at risk for type 1 diabetes born by Caesarean Section.

Children born by Caesarean Section have a higher risk for type 1 diabetes. We aimed to investigate whether Caesarean Section leads to alterations of the immune response in children with familial risk for type 1 diabetes. We examined measures of innate and adaptive immune responses in 94 prospectively followed children, including 40 born by Caesarean Section. Proinflammatory serum cytokine concentrations were determined at age 6 months. As a measure of vaccine response, IgG1, IgG2, and IgG4 tetanus antibody titers and CD4(+) T cell proliferation against tetanus toxoid were quantified. Compared to infants born by vaginal delivery, infants born by Caesarean Section had lower concentrations of the cytokines IFN-É£ (p=0.014) and IL-8 (p=0.005), and weaker CD4(+) T cell responses to tetanus measured in the first (p=0.007) and second year (p=0.047) of life. Overall, our findings provide evidence that the mode of delivery influences the immune status and responsiveness during childhood.

Reduced blood leukocyte and neutrophil numbers in the pathogenesis of type 1 diabetes.

Very little is known about the role of the innate immune system in the course of human type 1 diabetes. Here we investigated neutrophil numbers along with other leukocyte populations in patients at diagnosis of type 1 diabetes and during prediabetes. Complete and differential blood counts were analyzed from 107 adult patients with newly diagnosed type 1 diabetes, 21 children with persistent islet autoantibodies and a family history of type 1 diabetes, and 1 238 age and gender matched control subjects, all individuals without any signs of acute infection.Adult patients with newly diagnosed type 1 diabetes had significantly lower total WBC (p<1×10⁻6), neutrophil (p<1×10⁻6), basophil (p<1×10⁻6), monocyte (p=4×10⁻6) and lymphocyte (p<1×10⁻6) counts compared to control subjects. Erythrocyte, eosinophil and platelet counts did not differ between groups. Similarly, children with persistent islet autoantibodies had decreased WBC (p=0.001), neutrophils (p=0.003), and lymphocytes (p=0.006) in comparison to control children. Our findings demonstrate a perturbation of leukocyte homeostasis at and prior to onset of type 1 diabetes suggesting a general involvement of the innate immune system in the pathogenesis of type 1 diabetes.

Suppression of the nuclear factor Eny2 increases insulin secretion in poorly functioning INS-1E insulinoma cells.

Eny2, the mammalian ortholog of yeast Sus1 and drosophila E(y)2, is a nuclear factor that participates in several steps of gene transcription and in mRNA export. We had previously found that Eny2 expression changes in mouse pancreatic islets during the metabolic adaptation to pregnancy. We therefore hypothesized that the protein contributes to the regulation of islet endocrine cell function and tested this hypothesis in rat INS-1E insulinoma cells. Overexpression of Eny2 had no effect but siRNA-mediated knockdown of Eny2 resulted in markedly increased glucose and exendin-4-induced insulin secretion from otherwise poorly glucose-responsive INS-1E cells. Insulin content, cellular viability, and the expression levels of several key components of glucose sensing remained unchanged; however glucose-dependent cellular metabolism was higher after Eny2 knockdown. Suppression of Eny2 enhanced the intracellular incretin signal downstream of cAMP. The use of specific cAMP analogues and pathway inhibitors primarily implicated the PKA and to a lesser extent the EPAC pathway. In summary, we identified a potential link between the nuclear protein Eny2 and insulin secretion. Suppression of Eny2 resulted in increased glucose and incretin-induced insulin release from a poorly glucose-responsive INS-1E subline. Whether these findings extend to other experimental conditions or to in vivo physiology needs to be determined in further studies.

Reduced proliferation and a high apoptotic frequency of pancreatic beta cells contribute to genetically-determined diabetes susceptibility of db/db BKS mice.

Leptin receptor-deficient db/db mice are a commonly used research model and it is known that the genetic background, on which the mutation is bred, modulates the phenotype. While diabetes-resistant strains sustain near normal glycemia and hyperinsulinemia, susceptible backgrounds develop overt hyperglycemia and islet involution. We hypothesized that genetically-determined differences in the proliferative capacity and the apoptotic frequency of pancreatic beta cells contribute to this phenotypic disparity. We studied C57BLKS/J (BKS; diabetes-susceptible) and C57BL/6 (B6; diabetes-resistant) db/db mice and heterozygous controls from 5 to 12 weeks of age. Body weight, fasting blood glucose, plasma insulin, HOMA-IR, alpha cell mass, beta cell mass, proliferation and apoptosis were measured. Comparable insulin resistance developed in the 2 db/db strains, which was well compensated for on both genetic backgrounds until 7 weeks of age. As expected, the BKS mice became hyperglycemic at 9 weeks. Beta cell proliferation was initially increased in both db/db strains but decreased rapidly in the BKS mice with advancing age. The rate of beta cell apoptosis was already higher in prediabetic BKS mice than in their B6 counterparts. Beta cell mass increased continuously in the B6 strain until 12 weeks of age, but declined from 7 weeks onwards in BKS. An age-dependent decline of beta cell proliferation and an increased rate of beta cell apoptosis already in the prediabetic state probably contribute to the diabetes susceptibility of db/db BKS mice. These factors could also play a role in the genetic predisposition for type 2 diabetes in humans.

A general diffusion model for analyzing the efficacy of synaptic input to threshold neurons.

We describe a general diffusion model for analyzing the efficacy of individual synaptic inputs to threshold neurons. A formal expression is obtained for the system propagator which, when given an arbitrary initial state for the cell, yields the conditional probability distribution for the state at all later times. The propagator for a cell with a finite threshold is written as a series expansion, such that each term in the series depends only on the infinite threshold propagator, which in the diffusion limit reduces to a Gaussian form. This procedure admits a graphical representation in terms of an infinite sequence of diagrams. To connect the theory to experiment, we construct an analytical expression for the primary correlation kernel (PCK) which profiles the change in the instantaneous firing rate produced by a single postsynaptic potential (PSP). Explicit solutions are obtained in the diffusion limit to first order in perturbation theory. Our approximate expression resembles the PCK obtained by computer simulation, with the accuracy depending strongly on the mode of firing. The theory is most accurate when the synaptic input drives the membrane potential to a mean level more than one standard deviation below the firing threshold, making such cells highly sensitive to synchronous synaptic input.