To elucidate the mechanism of obesity-related insulin resistance, we investigated the impaired steps in the processes of phosphatidylinositol (PI) 3-kinase activation through binding with insulin receptor substrates 1 and 2 (IRS-1 and IRS-2) in liver and muscle of Zucker fatty rats. The expressions of IRS-1 and IRS-2 were shown to be downregulated in both liver and muscle in fatty rats (hepatic IRS-1, 83%; hepatic IRS-2, 45%; muscle IRS-1, 60%; muscle IRS-2, 78%), resulting in decreased tyrosine phosphorylation in response to insulin stimulation. Despite the decrease in the tyrosine phosphorylation levels of hepatic IRS-1 and IRS-2 being mild to moderate, associated PI 3-kinase activities were dramatically decreased in fatty rats (IRS-1, 14%; IRS-2, 10%), which may suggest alteration in the sites of phosphorylated tyrosine residues of hepatic IRS-1 and IRS-2. In addition, we demonstrated that the expressions of p85alpha and p55alpha regulatory subunits of PI 3-kinase were reduced (p85alpha, 67%; p55alpha, 54%), and that the p50alpha regulatory subunit was markedly upregulated (176%) in the livers of fatty rats without apparent alterations in expressions of the catalytic subunits p110alpha and p110beta. These alterations may reflect the obesity-related insulin resistance commonly observed in human NIDDM.

Summary Accumulating lines of evidence have suggested that regulatory T cells (Tregs) play a central role in T cell+ FoxP3 + T cells was significantly higher in patients with type 1A diabetes with detectable C-peptide but not in patients with type 1A diabetes without it and with fulminant type 1 diabetes. A proliferation suppression assay showed that a-Tregs were functionally impaired both in fulminant type 1 diabetes and in type 1A diabetes. In conclusion, a-Tregs were functionally impaired, related to residual insulin-secreting capacity and may be associated with the development of type 1 diabetes.

SummaryProgrammed cell death-1 (PD-1) is a co-stimulatory molecule that inhibits T cell proliferation. We aimed to clarify PD-1 expression in CD41 T cells and the association between PD-1 expression and the 7785C/T polymorphism of PDCD1, with a focus on the two subtypes of type 1 diabetes, type 1A diabetes (T1AD) and fulminant type 1 diabetes (FT1D), in the Japanese population. We examined 22 patients with T1AD, 15 with FT1D, 19 with type 2 diabetes (T2D) and 29 healthy control (HC) subjects. Fluorescence-activated cell sorting (FACS) and real-time PCR were utilized to analyse PD-1 expression quantitatively.Genotyping of 7785C/T in PDCD1 was performed using the TaqMan method in a total of 63 subjects (21 with T1AD, 15 with FT1D and 27 HC). FACS revealed a significant reduction in PD-1 expression in CD4 1T cells in patients with T1AD (mean: 4Á2 vs. 6Á0% in FT1D, P 5 0Á0450; vs. 5Á8% in T2D, P = 0Á0098; vs. 6Á0% in HC, P 5 0Á0018). PD-1 mRNA expression in CD4 1 T cells was also significantly lower in patients with T1AD than in the HC subjects. Of the 63 subjects, PD-1 expression was significantly lower in individuals with the 7785C/C genotype than in those with the C/T and T/T genotypes (mean: 4Á1 vs. 5Á9%, P 5 0Á0016). Our results indicate that lower PD-1 expression in CD4 1 T-cells might contribute to the development of T1AD through T cell activation.

abstract. Fulminant type 1 diabetes, established in 2000, is defined as a novel subtype of diabetes mellitus that results from remarkably acute and almost complete destruction of pancreatic beta cells at the disease onset. In this study, we aimed to clarify the pathogenesis of fulminant type 1 diabetes with special reference to insulitis and viral infection. We examined pancreatic autopsy samples from three patients who had died soon after the onset of disease and analyzed these by immunohistochemistry and in situ hybridization. The results were that both beta and alpha cell areas were significantly decreased in comparison with those of normal controls. Mean beta cell area of the patients just after the onset was only 0.00256 % while that of normal control was 1.745 %. Macrophages and T cells-but no natural killer cells-had infiltrated the islets and the exocrine pancreas. Although both of them had massively infiltrated, macrophages dominated islet infiltration and were detected in 92.6 % of the patients' islets. Toll-like receptor (TLR) 3, a sensor of viral components, was detected in 84.7±7.0 % of macrophages and 62.7±32.3 % of T cells (mean±SD) in all three patients. TLR7 and TLR9 were also detected in the pancreas of all three patients. enterovirus RNa was detected in beta-cell positive islets in one of the three patients by in situ hybridization. In conclusion, our results suggest that macrophage-dominated insulitis rather than T cell autoimmunity contributes to beta cell destruction in fulminant type 1 diabetes.