CTSH regulates ß-cell function and disease progression in newly diagnosed type 1 diabetes patients.

Over 40 susceptibility loci have been identified for type 1 diabetes (T1D). Little is known about how these variants modify disease risk and progression. Here, we combined in vitro and in vivo experiments with clinical studies to determine how genetic variation of the candidate gene cathepsin H (CTSH) affects disease mechanisms and progression in T1D. The T allele of rs3825932 was associated with lower CTSH expression in human lymphoblastoid cell lines and pancreatic tissue. Proinflammatory cytokines decreased the expression of CTSH in human islets and primary rat ß-cells, and overexpression of CTSH protected insulin-secreting cells against cytokine-induced apoptosis. Mechanistic studies indicated that CTSH exerts its antiapoptotic effects through decreased JNK and p38 signaling and reduced expression of the proapoptotic factors Bim, DP5, and c-Myc. CTSH overexpression also up-regulated Ins2 expression and increased insulin secretion. Additionally, islets from Ctsh(-/-) mice contained less insulin than islets from WT mice. Importantly, the TT genotype was associated with higher daily insulin dose and faster disease progression in newly diagnosed T1D patients, indicating agreement between the experimental and clinical data. In line with these observations, healthy human subjects carrying the T allele have lower ß-cell function, which was evaluated by glucose tolerance testing. The data provide strong evidence that CTSH is an important regulator of ß-cell function during progression of T1D and reinforce the concept that candidate genes for T1D may affect disease progression by modulating survival and function of pancreatic ß-cells, the target cells of the autoimmune assault.

Impaired coronary microcirculation in type 2 diabetic patients is associated with elevated circulating regulatory T cells and reduced number of IL-21R⁺ T cells.

BACKGROUND: Low-grade systemic inflammation is considered to participate in the progression of type 2 diabetes (T2D) and in diabetic complications. METHODS: To determine if circulating leukocytes were abnormally regulated in T2D patients, 8-color flow-cytometry (FACS) analysis was performed in a cross-sectional study of 37 T2D patients and 16 controls. Data obtained from the FACS analysis were compared to coronary flow reserve (CFR), assessed by Rb(82)-PET-imaging, to uncover inflammatory signatures associated with impaired CFR. RESULTS: Presence of T2D was associated with T cell attenuation characterized by reduced overall T cell, Th17, IL-21R(+), Treg's and TLR4(+) T cells, while the monocyte population showed enhanced TLR4 expression. Further, our data revealed reduced M1-like CD11c expression in T2D which was associated with impaired CFR. In contrast, we show, for the first time in T2D, increased TLR4 expression on CD8 T cells, increased Treg cell number and Treg maturation and reduced IL-21R expression on CD8 T cells to be functionally associated with impaired CFR. CONCLUSIONS: Our demonstration that HbA1c inversely correlates to several T cell populations suggests that T cells may play disease modulating roles in T2D. Further, the novel association between impaired CFR and regulatory T cells and IL-21R(+) T cells imply an intricate balance in maintaining tissue homeostasis in vascular diabetic complications.

No association between type 1 diabetes and genetic variation in vitamin D metabolism genes: a Danish study.

BACKGROUND: Vitamin D, certain single nucleotide polymorphisms (SNPs) in the vitamin D-receptor (VDR) gene and vitamin D metabolism genes have been associated with type 1 diabetes (T1D). OBJECTIVE: We wanted to examine if the most widely studied SNPs in genes important for production, transport, and action of vitamin D were associated with T1D or to circulating levels of vitamin D 25-hydroxyvitamin D [25(OH)D] in a juvenile Danish population. METHODS: We genotyped eight SNPs in five vitamin D metabolism genes in 1467 trios. 25(OH)D status were analyzed in 1803 children (907 patients and 896 siblings). RESULTS: We did not demonstrate association with T1D for SNPs in the following genes: CYP27B1, VDR, GC, CYP2R1, DHCR7, and CYP24A1. Though, variants in the GC gene were significantly associated with 25(OH)D levels in the joint model. CONCLUSION: Some of the most examined SNPs in vitamin D metabolism genes were not confirmed to be associated with T1D, though 25(OH) levels were associated with variants in the GC gene.

Huntingtin-interacting protein 14 is a type 1 diabetes candidate protein regulating insulin secretion and beta-cell apoptosis.

Type 1 diabetes (T1D) is a complex disease characterized by the loss of insulin-secreting ß-cells. Although the disease has a strong genetic component, and several loci are known to increase T1D susceptibility risk, only few causal genes have currently been identified. To identify disease-causing genes in T1D, we performed an in silico "phenome-interactome analysis" on a genome-wide linkage scan dataset. This method prioritizes candidates according to their physical interactions at the protein level with other proteins involved in diabetes. A total of 11 genes were predicted to be likely disease genes in T1D, including the INS gene. An unexpected top-scoring candidate gene was huntingtin-interacting protein (HIP)-14/ZDHHC17. Immunohistochemical analysis of pancreatic sections demonstrated that HIP14 is almost exclusively expressed in insulin-positive cells in islets of Langerhans. RNAi knockdown experiments established that HIP14 is an antiapoptotic protein required for ß-cell survival and glucose-stimulated insulin secretion. Proinflammatory cytokines (IL-1ß and IFN-γ) that mediate ß-cell dysfunction in T1D down-regulated HIP14 expression in insulin-secreting INS-1 cells and in isolated rat and human islets. Overexpression of HIP14 was associated with a decrease in IL-1ß-induced NF-κB activity and protection against IL-1ß-mediated apoptosis. Our study demonstrates that the current network biology approach is a valid method to identify genes of importance for T1D and may therefore embody the basis for more rational and targeted therapeutic approaches.

Induction of antigenic immune tolerance to delay type 1 diabetes - challenges for clinical translation.

PURPOSE OF REVIEW: Dissect the field of antigen-specific immunotherapy (ASIT) in type 1 diabetes (T1D), highlighting the major barriers currently blocking clinical translation. RECENT FINDINGS: ASIT remains a promising approach in T1D to re-establish the proper balance in the immune system to avoid the autoimmune-mediated attack or destruction of beta-cells in the pancreas. Despite some encouraging preclinical results, ASIT has not yet successfully translated into clinical utility, predominantly due to the lack of validated and clinically useful biomarkers. SUMMARY: To restore immune tolerance towards self-antigens, ASIT aims to establish a favourable balance between T effector cells and T regulatory cells. Whilst most ASITs, including systemic or oral administration of relevant antigens, have appeared safe in T1D, meaningful and durable preservation of functional beta-cell mass has not been proven clinically. Development, including clinical translation, remains negatively impacted by lack of predictive biomarkers with confirmed correlation between assay readout and clinical outcomes. To be able to address the high unmet medical need in T1D, we propose continued reinforced research to identify such biomarkers, as well efforts to ensure alignment in terms of trial design and conduct.

Hypoglycemia, S-ACE and ACE genotypes in a Danish nationwide population of children and adolescents with type 1 diabetes.

OBJECTIVE: High S-ACE levels have been shown to predispose to increased risk of hypoglycemia, however; some inconsistency relates to the risk of the ACE genotype. We investigated the association between S-ACE level at diagnosis and ACE genotype to long-term risk of severe hypoglycemia in more than 1000 children and adolescents with type 1 diabetes being part of the Danish Registry of Childhood diabetes over a 10-yr period. RESEARCH DESIGN AND METHODS: The Registry provided annual registration of clinical data, e.g., HbA1c, blood glucose monitoring, insulin type and dosage and acute diabetic complications (hypoglycemia and DKA). A BioBank coupled to the Registry comprised serum for measuring S-ACE levels and DNA for ACE genotyping. RESULTS: A total of 1037 individuals were included, aged 9.97 yr (SD 3.84). A total of 622 severe hypoglycemic episodes were observed in 270 individuals. Associations to increased risk of hypoglycemia generated from a negative binominal model were long diabetes duration (p < 0.0001) and high S-ACE level (p = 0.0497) when adjusted for ACE genotype. In the stratified analysis, S-ACE and insulin dosage were associated with hypoglycemia in girls (p = 0.026 and 0.028, respectively). An association of S-ACE level to ACE genotype was identified; however, no difference in the frequency of hypoglycemia, diabetes duration or HbA1c was demonstrated between ACE genotypes. CONCLUSION: This large nationwide cohort has identified an increased risk for hypoglycemia associated with higher S-ACE level, however only in girls. A strong association was found between ACE genotype and S-ACE levels, but ACE genotype was not related to risk of hypoglycemia.

Further evidence that mutations in INS can be a rare cause of Maturity-Onset Diabetes of the Young (MODY).

BACKGROUND: Insulin gene (INS) mutations have recently been described as a common cause of permanent neonatal diabetes (PNDM) and a rare cause of diabetes diagnosed in childhood or adulthood. METHODS: INS was sequenced in 116 maturity-onset diabetes of the young (MODYX) patients (n = 48 Danish and n = 68 Czech), 83 patients with gestational diabetes mellitus (GDM), 34 type 1 diabetic patients screened negative for glutamic acid decarboxylase (GAD), and 96 glucose tolerant individuals. The control group was randomly selected from the population-based sampled Inter99 study. RESULTS: One novel heterozygous mutation c.17G>A, R6H, was identified in the pre-proinsulin gene (INS) in a Danish MODYX family. The proband was diagnosed at 20 years of age with mild diabetes and treated with diet and oral hypoglycaemic agent. Two other family members who carried the INS R6H were diagnosed with diabetes when 51 years old and with GDM when 27 years old, respectively. A fourth mutation carrier had normal glucose tolerance when 20 years old. Two carriers of INS R6H were also examined twice with an oral glucose tolerance test (OGTT) with 5 years interval. They both had a approximately 30% reduction in beta-cell function measured as insulinogenic index. In a Czech MODYX family a previously described R46Q mutation was found. The proband was diagnosed at 13 years of age and had been treated with insulin since onset of diabetes. Her mother and grandmother were diagnosed at 14 and 35 years of age, respectively, and were treated with oral hypoglycaemic agents and/or insulin. CONCLUSION: Mutations in INS can be a rare cause of MODY and we conclude that screening for mutations in INS should be recommended in MODYX patients.

Linking glycemic dysregulation in diabetes to symptoms, comorbidities, and genetics through EHR data mining.

Diabetes is a diverse and complex disease, with considerable variation in phenotypic manifestation and severity. This variation hampers the study of etiological differences and reduces the statistical power of analyses of associations to genetics, treatment outcomes, and complications. We address these issues through deep, fine-grained phenotypic stratification of a diabetes cohort. Text mining the electronic health records of 14,017 patients, we matched two controlled vocabularies (ICD-10 and a custom vocabulary developed at the clinical center Steno Diabetes Center Copenhagen) to clinical narratives spanning a 19 year period. The two matched vocabularies comprise over 20,000 medical terms describing symptoms, other diagnoses, and lifestyle factors. The cohort is genetically homogeneous (Caucasian diabetes patients from Denmark) so the resulting stratification is not driven by ethnic differences, but rather by inherently dissimilar progression patterns and lifestyle related risk factors. Using unsupervised Markov clustering, we defined 71 clusters of at least 50 individuals within the diabetes spectrum. The clusters display both distinct and shared longitudinal glycemic dysregulation patterns, temporal co-occurrences of comorbidities, and associations to single nucleotide polymorphisms in or near genes relevant for diabetes comorbidities.

PTPN22 R620W functional variant in type 1 diabetes and autoimmunity related traits.

The PTPN22 gene, encoding the lymphoid-specific protein tyrosine phosphatase, a negative regulator in the T-cell activation and development, has been associated with the susceptibility to several autoimmune diseases, including type 1 diabetes. Based on combined case-control and family-based association studies, we replicated the finding of an association of the PTPN22 C1858T (R620W) functional variant with type 1 diabetes, which was independent from the susceptibility status at the insulin gene and at HLA-DR (DR3/4 compared with others). The risk contributed by the 1858T allele was increased in patients with a family history of other autoimmune diseases, further supporting a general role for this variant on autoimmunity. In addition, we found evidence for an association of 1858T allele with the presence of GAD autoantibodies (GADA), which was restricted to patients with long disease duration (>10 years, P < 0.001). This may help define a subgroup of patients with long-term persistence of GADA. The risk conferred by 1858T allele on GAD positivity was additive, and our meta-analysis also supported an additive rather than dominant effect of this variant on type 1 diabetes, similar to previous reports on rheumatoid arthritis and systemic lupus erythematosus.

A non-synonymous variant in SLC30A8 is not associated with type 1 diabetes in the Danish population.

Genome-wide association scans in type 2 diabetes (T2D) have identified a risk variant, rs13266634 (Arg325Trp), in SLC30A8 on chromosome 8. SLC30A8 encodes a beta-cell specific zinc-ion transporter and rs13266634 has been shown to affect insulin secretion. Recently, autoantibodies for Slc30A8 with high predictive value were demonstrated in individuals with type 1 diabetes (T1D), making this gene an interesting T1D candidate gene. We genotyped rs13266634 in 3008 cases and controls and 246 families from Denmark. Association to T1D could not be demonstrated.

CBLB variants in type 1 diabetes and their genetic interaction with CTLA4.

Type 1 diabetes (T1D) is a multifactorial disease with genetic and environmental components involved. Recent studies of an animal model of T1D, the Komeda diabetes-prone rat, have demonstrated that the Casitas-B-lineage lymphoma b (cblb) gene is a major susceptibility gene in the development of diabetes and other autoimmune features of this rat. As a result of the inhibitory role of Cbl-b in T cell costimulation, dysregulation of Cbl-b may also contribute to autoimmune diseases in man. Different isoforms of Cbl-b exist; we evaluated expression levels of two known transcript variants. Constitutive expression of both isoforms was demonstrated, as well as an increased expression, after cytokine exposure, of an isoform lacking exon 16, suggesting a possible role of this variant in the pathogenesis of autoimmunity. We screened coding regions of the human CBLB gene for mutations in a panel of individuals affected with several autoimmune diseases. Eight single nucleotide polymorphisms (SNPs) were detected. One SNP in exon 12 of the CBLB gene was significantly demonstrated to be associated to T1D in a large Danish T1D family material of 480 families. Evidence for common genetic factors underlying several autoimmune diseases has come from studies of cytotoxic T lymphocyte antigen 4 (CTLA4), which encodes another negatively regulatory molecule in the immune system. Gene-gene interactions probably play substantial roles in T1D susceptibility. We performed stratification of CBLB exon 12 SNP data, according to an established CTLA4 marker, CT60, and evidence for a genetic interaction between the CTLA4 and CBLB genes, involved in the same biological pathway of T cell receptor signaling, was observed.

Genetic Risk Score Modelling for Disease Progression in New-Onset Type 1 Diabetes Patients: Increased Genetic Load of Islet-Expressed and Cytokine-Regulated Candidate Genes Predicts Poorer Glycemic Control.

Genome-wide association studies (GWAS) have identified over 40 type 1 diabetes risk loci. The clinical impact of these loci on ß-cell function during disease progression is unknown. We aimed at testing whether a genetic risk score could predict glycemic control and residual ß-cell function in type 1 diabetes (T1D). As gene expression may represent an intermediate phenotype between genetic variation and disease, we hypothesized that genes within T1D loci which are expressed in islets and transcriptionally regulated by proinflammatory cytokines would be the best predictors of disease progression. Two-thirds of 46 GWAS candidate genes examined were expressed in human islets, and 11 of these significantly changed expression levels following exposure to proinflammatory cytokines (IL-1ß + IFNγ + TNFα) for 48 h. Using the GWAS single nucleotide polymorphisms (SNPs) from each locus, we constructed a genetic risk score based on the cumulative number of risk alleles carried in children with newly diagnosed T1D. With each additional risk allele carried, HbA1c levels increased significantly within first year after diagnosis. Network and gene ontology (GO) analyses revealed that several of the 11 candidate genes have overlapping biological functions and interact in a common network. Our results may help predict disease progression in newly diagnosed children with T1D which can be exploited for optimizing treatment.

Neutralizing Anti-IL20 Antibody Treatment Significantly Modulates Low Grade Inflammation without Affecting HbA1c in Type 2 Diabetic db/db Mice.

Low grade inflammation is present in pre-clinical and human type 2 diabetes. In this process, several cytokines like IL-1ß and inflammatory cells like macrophages are activated and demonstrated to participate to the disease initiation and progression. IL-20 is a cytokine known to play non-redundant roles in progression of several inflammatory diseases. To address the therapeutic effect of inhibiting the IL-20 pathway in diabetes, diabetic db/db mice were treated with neutralizing anti-IL20 antibodies in vivo and both metabolic and inflammatory parameters were followed. Diabetic islets expressed the IL-20 cytokine and all IL-20 receptor components in elevated levels compared to resting non-diabetic islets. Islets were responsive to ex vivo IL-20 stimulation measured as SOCS induction and KC and IL-6 production. Neutralizing anti-IL20 treatment in vivo had no effect on HbA1c or weight although the slope of blood glucose increase was lowered. In contrast, anti-IL20 treatment significantly reduced the systemic low-grade inflammation and modulated the local pancreatic immunity. Significant reduction of the systemic IL-1ß and MCP-1 was demonstrated upon anti-IL20 treatment which was orchestrated with a reduced RANTES, IL-16 and IL-2 but increased TIMP-1, MCP-1 and IL-6 protein expression locally in the pancreas. Interestingly, anti-IL20 treatment induced an expansion of the myeloid suppressor CD11bGr1int macrophage while reducing the number of CD8 T cells. Taken together, anti-IL20 treatment showed moderate effects on metabolic parameters, but significantly altered the low grade local and systemic inflammation. Hence, future combination therapies with anti-IL20 may provide beneficial therapeutic effects in type 2 diabetes through a reduction of inflammation.

Genetic Determinants of Enterovirus Infections: Polymorphisms in Type 1 Diabetes and Innate Immune Genes in the MIDIA Study.

Enteroviruses have been suggested as triggers of type 1 diabetes (T1D). We aimed to assess whether established T1D susceptibility single nucleotide polymorphisms (SNPs) and candidate SNPs in innate immune genes were associated with the frequency of enterovirus infection in otherwise healthy children. Fifty-six established T1D SNPs and 97 other candidate immunity SNPs were typed in 419 children carrying the T1D high-risk genotype, HLA-DR4-DQ8/DR3-DQ2 genotype, and 373 children without this genotype. Enteroviral RNA was detected using real-time polymerase chain reaction, with primers detecting essentially all enterovirus serotypes, in 7,393 longitudinal stool samples collected monthly (age range 3-36 months). The most significant association was with two T1D SNPs, rs12150079 (ZPBP2/ORMDL3/GSDMB region) (enterovirus frequency: AA 7.3%, AG 8.7%, GG 9.7%, RR = 0.86, overall p = 1.87E-02) and rs229541 (C1QTNF6/SSTR3/RAC2) (enterovirus frequency: CC 7.8%, CT 9.7%, TT 9.4%, RR = 1.13, overall p = 3.6E-02), followed by TLR8 (rs2407992) (p = 3.8E-02), TLR3 (1914926) (p = 4.9E-02), and two other T1D SNPs (IFIH1 rs3747517, p = 4.9E-02 and PTPN22, rs2476601, p = 5.3E-02). However, the quantile-quantile plot of p-values with confidence intervals for all 153 SNPs did not reveal clear evidence for rejection of the complete null hypothesis. Among a number of SNPs in candidate genes, we found no evidence for strong associations with enterovirus presence in stool samples from Norwegian children.

Application of genomics and proteomics in Type 1 diabetes pathogenesis research.

Type 1 diabetes is a polygenic, multifactorial autoimmune disease characterized by selective and irreversible destruction of the insulin-producing beta-cells in the pancreatic islets of Langerhans. An exogenous supply of insulin is required to sustain life after the onset of Type 1 diabetes. Despite decades of intensive research into its pathogenesis, no single gene or protein has been found to be responsible for Type 1 diabetes. This review will describe the use of large-scale genomics and proteomics in studying the pathogenesis of Type 1 diabetes, and will discuss future directions of research in the field.

Identification of novel type 1 diabetes candidate genes by integrating genome-wide association data, protein-protein interactions, and human pancreatic islet gene expression.

Genome-wide association studies (GWAS) have heralded a new era in susceptibility locus discovery in complex diseases. For type 1 diabetes, >40 susceptibility loci have been discovered. However, GWAS do not inevitably lead to identification of the gene or genes in a given locus associated with disease, and they do not typically inform the broader context in which the disease genes operate. Here, we integrated type 1 diabetes GWAS data with protein-protein interactions to construct biological networks of relevance for disease. A total of 17 networks were identified. To prioritize and substantiate these networks, we performed expressional profiling in human pancreatic islets exposed to proinflammatory cytokines. Three networks were significantly enriched for cytokine-regulated genes and, thus, likely to play an important role for type 1 diabetes in pancreatic islets. Eight of the regulated genes (CD83, IFNGR1, IL17RD, TRAF3IP2, IL27RA, PLCG2, MYO1B, and CXCR7) in these networks also harbored single nucleotide polymorphisms nominally associated with type 1 diabetes. Finally, the expression and cytokine regulation of these new candidate genes were confirmed in insulin-secreting INS-1 ß-cells. Our results provide novel insight to the mechanisms behind type 1 diabetes pathogenesis and, thus, may provide the basis for the design of novel treatment strategies.

Correlations between islet autoantibody specificity and the SLC30A8 genotype with HLA-DQB1 and metabolic control in new onset type 1 diabetes.

We hypothesised that the correlation between autoantibody specificity for the ZnT8 Arg325Trp isoforms and the type 2 diabetes-associated rs13266634 may affect ß-cell function at type 1 diabetes (T1D) onset. To study this, we tested 482 newly diagnosed diabetic probands and 478 healthy siblings from the Danish population-based T1D registry for autoantibodies to ZnT8 (ZnT8A) in addition to GAD65 and IA-2. The prevalence and titres of autoantibodies were correlated with genotypes for rs13266634 and HLA-DQB1, age at diagnosis (AAD) and insulin dose-adjusted HbA1c (IDAA1c), as a proxy for residual ß-cell function. We replicated the correlation between rs13266634 genotypes and specificity for the ZnT8-Argenine (ZnT8R) and ZnT8-Tryptophan (ZnT8W) isoforms previously reported. ZnT8A overlapped substantially with autoantibodies to glutamate decarboxylase 65 (GADA) and IA-2 (IA-2A) and correlated significantly with IA-2A prevalence (p < 2e-16). No effect on IDAA1c was demonstrated for ZnT8A or rs13266634. We found a correlation between ZnT8R positivity and HLA-DQB1*0302 genotypes (p = 0.016), which has not been shown previously. Furthermore, significantly lower ZnT8R and GADA prevalence and titres was found among probands with AAD < 5 years (prevalence: p = 0.004 and p = 0.0001; titres: p = 0.002 and p = 0.001, respectively). The same trend was observed for IA-2A and ZnT8W; however, the difference was non-significant. Our study confirms ZnT8 as a major target for autoantibodies at disease onset in our Danish T1D cohort of children and adolescents, and we have further characterised the relationship between autoantibody specificity for the ZnT8 Arg325Trp epitopes and rs13266634 in relation to established autoantibodies, AAD, measures of ß-cell function and HLA-DQB1 genotypes in T1D.

Relationship between ZnT8Ab, the SLC30A8 gene and disease progression in children with newly diagnosed type 1 diabetes.

Autoantibodies against the newly established autoantigen in type 1 diabetes, zinc transporter 8, ZnT8, are presented as two types, ZnT8RAb and ZnT8WAb. The rs13266634 variant of the SLC30A8 gene has recently been found to determine the type of ZnT8Ab. The aim of this study was to explore the impact of this genetic variant and the ZnT8Ab on the residual beta-cell function during disease progression the first year after disease diagnosis in children with newly diagnosed type 1 diabetes. This cohort consists of 257 children aged < 16 years, all patients were newly diagnosed with type 1 diabetes. A Boost-test was carried out at 1, 6, and 12 months to characterize the residual beta-cell function. Carriers of the CC and CT genotype groups of the rs13266634 SNP of the SLC30A8 gene had higher stimulated C-peptide levels the first year after onset compared with those of the TT genotype group (29%, p = 0.034). CC genotype carriers were highly associated with the presence of ZnT8RAb subtype during disease progression (compared with TT, p < 0.0001). On the other hand, the TT genotype was associated with the presence of ZnT8WAb subtype during disease progression (compared with CC, p < 0.0001). The C allele of the SLC30A8 gene is associated with preserved beta-cell function in type 1 diabetes patients. The genetic determination of the rs13266634 variant on the ZnT8Ab specificity is sustained the first 12 months after the diagnosis of type 1 diabetes in a pediatric cohort.

The type 1 diabetes - HLA susceptibility interactome--identification of HLA genotype-specific disease genes for type 1 diabetes.

BACKGROUND: The individual contribution of genes in the HLA region to the risk of developing type 1 diabetes (T1D) is confounded by the high linkage disequilibrium (LD) in this region. Using a novel approach we have combined genetic association data with information on functional protein-protein interactions to elucidate risk independent of LD and to place the genetic association into a functional context. METHODOLOGY/PRINCIPAL FINDINGS: Genetic association data from 2300 single nucleotide polymorphisms (SNPs) in the HLA region was analysed in 2200 T1D family trios divided into six risk groups based on HLA-DRB1 genotypes. The best SNP signal in each gene was mapped to proteins in a human protein interaction network and their significance of clustering in functional network modules was evaluated. The significant network modules identified through this approach differed between the six HLA risk groups, which could be divided into two groups based on carrying the DRB1*0301 or the DRB1*0401 allele. Proteins identified in networks specific for DRB1*0301 carriers were involved in stress response and inflammation whereas in DRB1*0401 carriers the proteins were involved in antigen processing and presentation. CONCLUSIONS/SIGNIFICANCE: In this study we were able to hypothesise functional differences between individuals with T1D carrying specific DRB1 alleles. The results point at candidate proteins involved in distinct cellular processes that could not only help the understanding of the pathogenesis of T1D, but also the distinction between individuals at different genetic risk for developing T1D.