Recruiting young pre-symptomatic children for a clinical trial in type 1 diabetes: Insights from the Fr1da insulin intervention study.

BACKGROUND: Although detection of children at high risk of developing type 1 diabetes and diagnosis of early stages is possible, up to now there exists no approved therapy to delay or prevent type 1 diabetes. Thus it is vital to develop evidence-based interventions. For this a sufficient number of trial participants is crucial but difficult to obtain especially in asymptomatic children. AIM: Identifying family characteristics that lead to or impede trial participation and analyze reasons stated by families for non-participation. METHODS: Participants for the Fr1da Insulin Intervention study are recruited from the Fr1da study, a population based screening for early stage type 1 diabetes in Bavaria. Families with eligible children were invited to enroll. We analyzed sex and age of the child, distance of the family to the study center in Munich and the existence of a first degree family member with type 1 as possible influential factors for study participation. We also analyzed reasons stated by families who declined study participation in a phone interview. RESULTS: Of 146 eligible children 77 (53%) were enrolled into the trial. None of the tested family characteristics differed significantly between the enrolling and the families not participating, but in general enrolling families lived closer to the study site than families not participating. This is also reflected in the reasons given by non-participating families. The most frequent reason stated were time restrictions. The second most frequent reason was the venous blood draw. CONCLUSION: The factors for non-participation identified in this project need be taken into account for the design of future trials in young children to ensure proper recruitment and thus to generate valid results for medical treatment of children. More research on the reason of participation and non-participation in clinical trials is needed.

Fasting hypoglycemia is associated with disease progression in presymptomatic early stage type 1 diabetes.

OBJECTIVE: In children with presymptomatic type 1 diabetes, intermittent hyperglycemia and rising hemoglobin A1c levels are a known signal of progression toward insulin-dependency. Episodes of hypoglycemia, however, have also been reported in one published case. We investigated the prevalence of hypoglycemia and its association with disease progression in children with presymptomatic type 1 diabetes. METHODS: We compared the frequency of hypoglycemic fasting blood glucose levels (<60 mg/dL) in 48 autoantibody negative and 167 multiple ß-cell autoantibody positive children aged 2 to 5 years. We classified the autoantibody positive children into three categories based on their glucose levels in fasting state (hypoglycemic [<60 mg/dL], normoglycemic [60-99 mg/dL] or hyperglycemic [≥100 mg/dL]). We then compared the glucose levels under challenge during oral glucose tolerance tests (OGTTs) between the three categories. RESULTS: In the autoantibody positive children, 5.1% of the fasting samples were hypoglycemic, while in the autoantibody negative children no hypoglycemia was observed. Hypoglycemia occurred more often in autoantibody positive children who had already entered stage 2 or stage 3 of type 1 diabetes than in stage 1 patients (P = 0.02). Children who had hypoglycemic compared to normoglycemic fasting blood glucose values had higher 120-minute blood glucose values under OGTT challenge, and a higher rate of pathological OGTTs (P = 0.04). CONCLUSIONS: Fasting hypoglycemia seems to be an indicator of disease progression in presymptomatic type 1 diabetes and may therefore represent a novel marker for the identification of children who should be monitored more closely for progression toward insulin-dependent type 1 diabetes.

GM-CSF producing autoreactive CD4+ T cells in type 1 diabetes.

The phenotype of autoreactive T cells in type 1 diabetes is described as Th1, Th17 and/or Th21, but is largely uncharacterized. We combined multi-parameter cytokine profiling and proliferation, and identified GM-CSF producing cells as a component of the response to beta cell autoantigens proinsulin and GAD65. Overall cytokine profiles of CD4+ T cell were not altered in type 1 diabetes. In contrast, patients with recent onset type 1 diabetes had increased frequencies of proinsulin-responsive CD4+CD45RA- T cells producing GM-CSF (p=0.002), IFNγ (p=0.004), IL-17A (p=0.008), IL-21 (p=0.011), and IL-22 (p=0.007), and GAD65-responsive CD4+CD45RA- T cells producing IL-21 (p=0.039). CD4+ T cells with a GM-CSF+IFNγ-IL-17A-IL-21-IL-22- phenotype were increased in patients for responses to both proinsulin (p=0.006) and GAD65 (p=0.037). GM-CSF producing T cells are a novel phenotype in the repertoire of T helper cells in type 1 diabetes and consolidate a Th1/Th17 pro-inflammatory pathogenesis in the disease.

The C-terminal region of the meiosis-specific protein kinase Ime2 mediates protein instability and is required for normal spore formation in budding yeast.

The cyclin-dependent kinase Cdk1 and the related kinase Ime2 act in concert to trigger progression of the meiotic cell cycle in the yeast Saccharomyces cerevisiae. These kinases share several functions and substrates during meiosis, but their regulation seems to be clearly different. In contrast to Cdk1, no cyclin seems to be involved in the regulation of Ime2 activity. Ime2 is a highly unstable protein, and we aimed to elucidate the relevance of Ime2 instability. We first determined the sequence elements required for Ime2 instability by constructing a set of deletions in the IME2 gene. None of the small deletions in Ime2 affected its instability, but deletion of a 241 amino acid C-terminal region resulted in a highly stabilized protein. Thus, the C-terminal domain of Ime2 is important for mediating protein instability. The stabilized, truncated Ime2 protein is highly active in vivo. Replacement of the IME2 gene with the truncated IME2DeltaC241 in diploid strains did not interfere with meiotic nuclear divisions, but caused abnormalities in spore formation, as manifested by the appearance of many asci with a reduced spore number such as triads and dyads. The truncated Ime2 caused a reduction of spore number in a dominant manner. We conclude that downregulation of Ime2 kinase activity mediated by the C-terminal domain is required for the efficient production of normal four-spore asci. Our data suggest a role for Ime2 in spore number control in S. cerevisiae.

Distinct domains of yeast cortical tag proteins Bud8p and Bud9p confer polar localization and functionality.

In Saccharomyces cerevisiae, diploid yeast cells follow a bipolar budding program, which depends on the two transmembrane glycoproteins Bud8p and Bud9p that potentially act as cortical tags to mark the cell poles. Here, we have performed systematic structure-function analyses of Bud8p and Bud9p to identify functional domains. We find that polar transport of Bud8p and Bud9p does not depend on N-terminal sequences but instead on sequences in the median part of the proteins and on the C-terminal parts that contain the transmembrane domains. We show that the guanosine diphosphate (GDP)/guanosine triphosphate (GTP) exchange factor Bud5p, which is essential for bud site selection and physically interacts with Bud8p, also interacts with Bud9p. Regions of Bud8p and Bud9p predicted to reside in the extracellular space are likely to confer interaction with the N-terminal region of Bud5p, implicating indirect interactions between the cortical tags and the GDP/GTP exchange factor. Finally, we have identified regions of Bud8p and Bud9p that are required for interaction with the cortical tag protein Rax1p. In summary, our study suggests that Bud8p and Bud9p carry distinct domains for delivery of the proteins to the cell poles, for interaction with the general budding machinery and for association with other cortical tag proteins.

Role of Cdc42-Cla4 interaction in the pheromone response of Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, the highly conserved Rho-type GTPase Cdc42 is essential for cell division and controls cellular development during mating and invasive growth. The role of Cdc42 in mating has been controversial, but a number of previous studies suggest that the GTPase controls the mitogen-activated protein (MAP) kinase cascade by activating the p21-activated protein kinase (PAK) Ste20. To further explore the role of Cdc42 in pheromone-stimulated signaling, we isolated novel alleles of CDC42 that confer resistance to pheromone. We find that in CDC42(V36A) and CDC42(V36A, I182T) mutant strains, the inability to undergo pheromone-induced cell cycle arrest correlates with reduced phosphorylation of the mating MAP kinases Fus3 and Kss1 and with a decrease in mating efficiency. Furthermore, Cdc42(V36A) and Cdc42(V36A, I182T) proteins show reduced interaction with the PAK Cla4 but not with Ste20. We also show that deletion of CLA4 in a CDC42(V36A, I182T) mutant strain suppresses pheromone resistance and that overexpression of CLA4 interferes with pheromone-induced cell cycle arrest and MAP kinase phosphorylation in CDC42 wild-type strains. Our data indicate that Cla4 has the potential to act as a negative regulator of the mating pathway and that this function of the PAK might be under control of Cdc42. In conclusion, our study suggests that control of pheromone signaling by Cdc42 not only depends on Ste20 but also involves interaction of the GTPase with Cla4.