Identification of a Molecular Signature in Human Type 1 Diabetes Mellitus Using Serum and Functional Genomics

Abstract

Understanding active proinflammatory mechanisms at and before type 1 diabetes mellitus (T1DM) onset is hindered in humans, given that the relevant tissues are inaccessible and pancreatic immune responses are difficult to measure in the periphery by traditional approaches. Therefore, we investigated the use of a sensitive and comprehensive genomics strategy to investigate the presence of proinflammatory factors in serum. The sera of recent onset diabetes patients (n = 15, 12 possessing and 3 lacking islet cell autoantibodies), long-standing diabetes patients (n = 12), “at risk” siblings of diabetes patients (n = 9), and healthy controls (n = 12) were used to induce gene expression in unrelated, healthy PBMC. After culture, gene expression was measured with microarrays and normalized expression data were subjected to hierarchical clustering and multidimensional scaling. All recent onset sera induced an expression signature (192 UniGenes; fold change: >1.5, p < 0.01; false discovery rate: <0.01) that included IL-1 cytokine family members and chemokines involved in monocyte/macrophage and neutrophil chemotaxis, as well as numerous receptors and signaling molecules. This molecular signature was not induced with the sera of healthy controls or long standing diabetes patients, where longitudinal analysis of “at risk” siblings (n = 3) before and after onset support the hypothesis that the signature emerges years before onset. This study supports prior investigations of serum that reflect disease processes associated with progression to T1DM. Identification of unique inflammatory mediators may improve disease prediction beyond current islet autoantibodies. Furthermore, proinflammatory serum markers may be used as inclusion criteria or endpoint measures in clinical trials aimed at preventing T1DM.

Specific gene expression signature associated with development of autoimmune type-I diabetes using whole-blood microarray analysis

“…Recently, it was shown that incubation of peripheral blood mononuclear cells of healthy blood donors with the sera of recent-onset T1D or PT1D results in the expression of IFN-induced genes, leading to the hypothesis that the IFN signature emerges years before the onset of T1D. 7 In our study, type-I IFN gene expression was not detected in blood. This suggests that the type-I IFN gene is slightly expressed in blood.…”

“…5 Genome-wide gene expression profiling using microarrays is a powerful technology. It was recently applied to the prediction of the outcome of T1D 7 and the identification of genes and pathways dysregulated 8 from the analysis of peripheral blood mononuclear cells of T1D patients. However, this approach has never been employed directly on peripheral whole-blood cells.…”

Distinct Monocyte Gene-Expression Profiles in Autoimmune Diabetes

“…A recent study (24) showed that factors in serum of type 1 diabetic patients could induce inflammatory genes (CCL2, CCL7, IL1B) in peripheral blood mononuclear cells (PBMCs). Another gene expression study of PBMCs of type 1 diabetic patients (25) also detected overexpression of inflammatory genes (among others, IL1B and PTGS2), without evidence of the extended signatures described here.…”

Immunology of β-Cell Destruction

“…Some reports have found poor in vitro maturation and pro-in ammatory cytokine response in DC from children at genetic risk for TID [389,390] and a number of attested T-cell responses from PBMC of at-risk subjects toward islet-specific autoantigens GAD65 [318,319] and insulin/proinsulin [318,328]. Finally, increased chemokines, such as CXCl10 [354] and adhesion molecules [356], have been detected in the plasma of at-risk individuals; more recently, in three at-risk subjects followed until diagnosis these alterations were present years before the clinical onset [367]. However, this data cannot to date be translated into risk stratification.…”

“…Two studies in the mouse have suggested that, regardless the provenience of the T cells (periphery, islets, or lymph nodes), ß-cell antigen-specific CD8+ T-cell pool shares TCR chain usage [365] and show conserved patterns of epitope immunodominance [366]. Another study has performed micro array analysis of the cytokine pattern of PBMC from healthy subjects after the exposure to sera from new-onset T1D patients and has reported an enhanced secretion of pro-in ammatory factors as IL-1, CCl2, and CCl7 [367].…”