Type 1 diabetes islet autoantibody markers

Viruses as a potential environmental trigger of type 1 diabetes mellitus (Review)

The etiopathogenesis of type 1 diabetes mellitus (T1DM) is a complex multifactorial process that involves an intricate network of genetic, epigenetic, immunological, and environmental factors. Despite the advances in recent years, some aspects of the mechanisms involved in triggering the disease are still unclear. Infections with certain viruses have been suggested as possible environmental triggers for the autoimmune process that leads to selective and progressive destruction of pancreatic β-cells and insufficiency of insulin production, which is its hallmark. In this review, advances in knowledge and evidence that suggest the participation of certain viruses in the mechanisms of disease initiation and progression are described. It has been accepted that environmental factors, including viruses, can initiate and possibly sustain, accelerate, or slow down the autoimmune process and consequently damage insulin-producing pancreatic β-cells. Although the role of these agents, especially human enteroviruses, has been exhaustively studied as the most likely triggers of the activation of autoimmunity that destroys pancreatic islets and leads to T1DM, certain doubts remain. Clinical epidemiological and experimental studies in humans and animals provide consistent and increasing evidence that persistent viral infections, especially with human enteroviruses and rotavirus infections, are associated with an increased risk of the disease in individuals genetically predisposed to autoimmunity.

Autoantibodies to Zinc Transporter 8 and SLC30A8 Genotype in Type 1 Diabetes Childhood: A Pioneering Study in North Africa

BACKGROUND

Type 1 diabetes (T1D) occurs as a result of insulin deficiency due to destructive lesions of pancreatic β cells. In addition to classical autoantibodies (Abs) to islet cell antigens, antizinc transporter 8 Abs (ZnT8-Ab) have been recently described in T1D.

OBJECTIVE

As no data on ZnT8-Ab in Tunisian patients has been reported, we aim to evaluate the relationships between ZnT8-Ab, ZnT8 coding gene (SLC30A8) promoter polymorphism, and T1D risk in newly diagnosed children.

METHODS

ZnT8-Ab were measured in the serum of T1D newly affected children (n = 156) who were admitted to the pediatric department of the Hedi Chaker University Hospital of Sfax. Rs13266634 was genotyped in T1D children and 79 of their first-degree parents. The SPSS software was used to analyze the serological data. Allelic association analysis was conducted with family-based association tests implemented in the FBAT program v1.5.1.

RESULTS

ZnT8-Ab was detected in 66/156 (42.3%) of T1D newly diagnosed children. Among them, 6 (9%) presented ZnT8-Ab as the only humoral marker. The inclusion of ZnT8-Ab increased the number of Ab-positive patients to 90% and reduced the negative ones by 27%. There was no evidence of any overtransmission of any allele of the rs13266634 C/T polymorphism from parents to affected T1D children, nor of any correlation with any clinical or serological parameter. After the T1D disease onset age adjustment, a significant association was observed with the C allele suggesting that it could have a susceptibility role.

CONCLUSION

ZnT8-Ab appears as a relevant diagnostic marker for T1D in Tunisian children, especially at the onset of the disease as teenagers.

Epigenetic Contribution to the Development and Progression of Vascular Diabetic Complications

SIGNIFICANCE

The number of people suffering from diabetes worldwide is steadily rising. Complications from diabetes, including cardiovascular and renal disease, contribute to the high morbidity and mortality associated with this disease. Recent Advances: Hyperglycemia promotes tissue damage through diverse mechanisms involving increased production of reactive oxygen species. Increased oxidative stress drives changes in chromatin structure that mediate gene expression changes leading to the upregulation of proinflammatory and profibrotic mediators. The epigenetic contribution to diabetes-induced changes in gene expression is increasingly recognized as a key factor in the development and progression of vascular diabetic complications.

CRITICAL ISSUES

The mechanisms through which stimuli from the diabetic milieu promote epigenetic changes remain poorly understood. In addition, glycemic control constitutes an important factor influencing epigenetic states in diabetes, and the phenomenon of hyperglycemic memory warrants further research.

FUTURE DIRECTIONS

Knowledge of the molecular mechanisms underlying epigenetic changes in diabetes may allow the design of novel therapeutic strategies to reduce the burden of diabetic complications. Furthermore, certain epigenetic markers are detected early during the onset of diabetes and its complications and may prove useful as biomarkers for disease risk prediction.

Two Novel MicroRNA Biomarkers Related to β-Cell Damage and Their Potential Values for Early Diagnosis of Type 1 Diabetes

CONTEXT

New strategies and biomarkers are needed in the early detection of β-cell damage in the progress of type 1 diabetes mellitus (T1DM).

OBJECTIVE

To explore whether serum microRNAs (miRNA) should be served as biomarkers for T1DM.

DESIGN, SETTINGS, AND PATIENTS

The miRNA profile was established with miRNA microarray in discovery phase (six T1DM, six controls). A miRNA-based model for T1DM diagnosis was developed using logistic regression analysis in the training dataset (40 T1DM, 56 controls) and then validated with leave-one-out cross validation and another independent validation dataset (33 T1DM, 29 controls).

MAIN OUTCOME MEASURES

Quantitative reverse transcription polymerase chain reaction was applied to confirm the differences of candidate miRNAs between T1DM and controls. Area under the receiver-operating characteristic (ROC) curve (AUC) was used to evaluate diagnostic accuracy. INS-1 cells, streptozotocin-treated mice (n = 4), and nonobese diabetic (NOD) mice (n = 12) were used to evaluate the association of miRNAs with β-cell damage.

RESULTS

A miRNA -based model was established in the training dataset with high diagnostic accuracy for T1DM (AUC = 0.817) based on six candidate differential expressed miRNAs identified in discovery phase. The validation dataset showed the model's satisfactory diagnostic performance (AUC = 0.804). Secretions of miR-1225-5p and miR-320c were significantly increased in streptozotocin-treated mice and INS-1 cells. Noteworthy, the elevation of these two miRNAs was observed before glucose elevation in the progress of diabetes in NOD mice.

CONCLUSIONS

Two miRNA biomarkers (miR-1225-5p and miR-320c) related to β-cell damage were identified in patients with recent-onset T1DM. The miRNA-based model established in this study exhibited a good performance in diagnosis of T1DM.

Autoantibodies against zinc transporter 8 are related to age and metabolic state in patients with newly diagnosed autoimmune diabetes

AIMS

To assess the prevalence of ZnT8-ab and its correlation to other autoimmune markers and diabetic ketoacidosis occurrence in children and adults with T1DM onset.

METHODS

The study included 367 patients (218 children; 149 adults) at the T1DM onset. Selected diabetes-related autoantibodies such as GAD-ab, IA2-ab, ZnT8-ab were tested before the initiation of insulin therapy. Diabetic ketoacidosis was defined as glucose concentration > 13.9 mmol/l, pH < 7.30, concentration of HCO₃ < 15 mmol/l, presence of ketone bodies in the blood and urine.

RESULTS

The autoantibodies pattern differs in both study groups. Children were mostly positive for two (37.8%) and three (49.5%) autoantibodies, whereas adults for one (32.2%) and two (30.7%). The most frequently detected autoantibodies in youth were ZnT8-ab (81.1%) and IA2-ab (80.7%), while in adults GAD-ab (74.8%). ZnT8-ab (p < 0.0001) titers were significantly higher in children, but adults had higher titer of GAD-ab (p < 0.0001) and IA2-ab (p < 0.0001). Children developed more frequently diabetic ketoacidosis (28.4 vs. 10.7%, p = 0.0002). ZnT8-ab (p = 0.002) and IA2-ab (p = 0.008) were reported mostly in individuals with ketoacidosis. A correlation between the number of positive antibodies and the severity of ketoacidosis was observed (R_s - 0.129 p = 0.014). ZnT8-ab were associated with a greater risk of ketoacidosis independent of gender, age group and the autoantibodies number [OR = 2.44 (95% CI 1.0-5.94), p = 0.04].

CONCLUSIONS

Children are at greater risk of ketoacidosis at the diagnosis of diabetes. ZnT8-ab and IA2-ab are commonly detected in children, while adults have frequently higher titer of GAD-ab. ZnT8-ab are associated with more acute diabetes onset.

miRNAs: Nanomachines That Micromanage the Pathophysiology of Diabetes Mellitus

Diabetes mellitus (DM) refers to a combination of heterogeneous complex metabolic disorders that are associated with episodes of hyperglycemia and glucose intolerance occurring as a result of defects in insulin secretion, action, or both. The prevalence of DM is increasing at an alarming rate, and there exists a need to develop better therapeutics and prognostic markers for earlier detection and diagnosis. In this review, after giving a brief introduction of diabetes mellitus and microRNA (miRNA) biogenesis pathway, we first describe various in vitro and animal model systems that have been developed to study diabetes. Further, we elaborate on the significant roles played by miRNAs as regulators of gene expression in the context of development of diabetes and its secondary complications. The different approaches to quantify miRNAs and their potential to be used as therapeutic targets for alleviation of diabetes have also been discussed.

The course of diabetes in children, adolescents and young adults: does the autoimmunity status matter?

BACKGROUND

Initial classification of diabetes of young may require revision to improve diagnostic accuracy of different forms of diabetes. The aim of our study was to examine markers of beta-cell autoimmunity in a cohort of young (0-25 years) patients with type 1 diabetes and compare the presentation and course of the disease according to the presence of pancreatic antibodies.

METHODS

Cross-sectional population-based study was performed covering 100% of pediatric (n = 860) and 70% of 18-25 years old adult patients (n = 349) with type 1 diabetes in Lithuania.

RESULTS

No antibodies (GAD65, IA-2, IAA and ICA) were found in 87 (7.5%) cases. Familial history of diabetes was more frequent in those with antibodies-negative diabetes (24.1 vs. 9.4%, p < 0.001). Gestational age, birth weight and age at diagnosis was similar in both groups. Ketosis at presentation was more frequent in patients with autoimmune diabetes (88.1 vs. 73.5%, p < 0.05). HbA1c at the moment of investigation was 8.6 (3) vs. 8.7 (2.2)% in antibodies-negative and antibodies-positive diabetes groups, respectively, p > 0.05. In the whole cohort, neuropathy was found in 8.8% and nephropathy - in 8.1% of cases, not depending on autoimmunity status. Adjusted for age at onset, disease duration and HbA1c, retinopathy was more frequent in antibodies-negative subjects (13.8 vs. 7.8%, p < 0.05).

CONCLUSION

Antibodies-negative pediatric and young adult patients with type 1 diabetes in this study had higher incidence of family history of diabetes, higher frequency of retinopathy, less frequent ketosis at presentation, but similar age at onset, HbA1c, incidence of nephropathy and neuropathy compared to antibodies-positive patients.

Organ donor specimens: What can they tell us about type 1 diabetes?

Type 1 diabetes (T1D) is a chronic disease resulting from the destruction of pancreatic beta cells, due to a poorly understood combination of genetic, environmental, and immune factors. The JDRF Network for Pancreatic Organ donors with Diabetes (nPOD) program recovers transplantation quality pancreas from organ donors throughout the USA. In addition to recovery of donors with T1D, non-diabetic donors include those with islet autoantibodies. Donors with type 2 diabetes and other conditions are also recovered to aid investigations directed at the full spectrum of pathophysiological mechanisms affecting beta cells. One central processing laboratory conducts standardized procedures for sample processing, storage, and distribution, intended for current and future cutting edge investigations. Baseline histology characterizations are performed on the pancreatic samples, with images of the staining results provided though whole-slide digital scans. Uniquely, these high-grade biospecimens are provided without expense to investigators, working worldwide, seeking methods for disease prevention and reversal strategies. Collaborative working groups are highly encouraged, bringing together multiple investigators with different expertise to foster collaborations in several areas of critical need. This mini-review will provide some key histopathological findings emanating from the nPOD collection, including the heterogeneity of beta cell loss and islet inflammation (insulitis), beta cell mass, insulin-producing beta cells in chronic T1D, and pancreas weight reductions at disease onset. Analysis of variations in histopathology observed from these organ donors could provide for mechanistic differences related to etiological agents and serve an important function in terms of identifying the heterogeneity of T1D.

Circulating microRNAs as novel biomarkers for diabetes mellitus

Diabetes mellitus is characterized by insulin secretion from pancreatic β cells that is insufficient to maintain blood glucose homeostasis. Autoimmune destruction of β cells results in type 1 diabetes mellitus, whereas conditions that reduce insulin sensitivity and negatively affect β-cell activities result in type 2 diabetes mellitus. Without proper management, patients with diabetes mellitus develop serious complications that reduce their quality of life and life expectancy. Biomarkers for early detection of the disease and identification of individuals at risk of developing complications would greatly improve the care of these patients. Small non-coding RNAs called microRNAs (miRNAs) control gene expression and participate in many physiopathological processes. Hundreds of miRNAs are actively or passively released in the circulation and can be used to evaluate health status and disease progression. Both type 1 diabetes mellitus and type 2 diabetes mellitus are associated with distinct modifications in the profile of miRNAs in the blood, which are sometimes detectable several years before the disease manifests. Moreover, circulating levels of certain miRNAs seem to be predictive of long-term complications. Technical and scientific obstacles still exist that need to be overcome, but circulating miRNAs might soon become part of the diagnostic arsenal to identify individuals at risk of developing diabetes mellitus and its devastating complications.

Residual C-peptide in patients with Type 1 diabetes and multiethnic backgrounds

OBJECTIVE

To evaluate serum C-peptide in 88 patients from a multiethnic population with Type-1 diabetes and variable disease durations.

METHOD

Eighty-eight patients with a mean disease duration of 8.1 +7.6 years were included and underwent C-peptide measurement before and after glucagon stimulation. Chi-squared and Mann Whitney U-tests were used to compare the variables between groups (all two-tailed, α = 0.05). Spearmans correlation coefficient was used to test the association between the continuous variables. Logistic regression was used for the multivariate analysis. Twenty-eight (31.8%) individuals had significantly detectable C-peptide levels after stimuli, particularly those with a shorter disease duration (p<0.001).

RESULTS

Patients with detectable C-peptide levels required lower insulin doses (p<0.009) and had similar HbA1C results (p = 0.182) and fewer chronic complications (p = 0.029).

CONCLUSION

C-peptide detection was common in Type-1 diabetics, particularly shortly after being diagnosed. This result may have clinical implications.

GADA titer-related risk for organ-specific autoimmunity in LADA subjects subdivided according to gender (NIRAD study 6)

CONTEXT

Latent autoimmune diabetes in adults (LADA) includes a heterogeneous population wherein, based on glutamic acid decarboxylase antibody (GADA) titer, different subgroups of subjects can be identified.

OBJECTIVE

The aim of the present study was to evaluate GADA titer-related risk for β-cell and other organ-specific autoimmunity in LADA subjects.

METHODS

Adult-onset autoimmune diabetes subjects (n=236) and type 2 diabetes (T2DM) subjects (n=450) were characterized for protein tyrosine phosphatase (IA-2IC and IA-2(256-760)), zinc transporter 8 (ZnT8), thyroid peroxidase, (TPO), steroid 21-hydroxylase (21-OH), tissue transglutaminase (tTG), and antiparietal cell (APC) antibodies.

RESULTS

High GADA titer compared to low GADA titer showed a significantly higher prevalence of IA-2IC, IA-2(256-760), ZnT8, TPO, and APC antibodies (P≤0.04 for all comparison). 21-OH antibodies were detected in 3.4% of high GADA titer. A significant decreasing trend was observed from high GADA to low GADA and to T2DM subjects for IA-2(256-760), ZnT8, TPO, tTG, and APC antibodies (P for trend≤0.001). TPO was the only antibody showing a different prevalence between gender; low GADA titer and T2DM female patients had a higher frequency of TPO antibody compared to males (P=0.0004 and P=0.0006, respectively), where the presence of high GADA titer conferred an odds ratio of 8.6 for TPO compared to low GADA titer. After subdividing high and low GADA titer subjects according to the number of antibodies, we observed that 73.3% of high GADA titer subjects were positive for at least one or more antibodies, compared to 38.3% of low GADA titer (P<0.0001).

CONCLUSIONS

In LADA subjects, high GADA titer was associated with a profile of more severe autoimmunity and, in male gender, specifically predisposed to thyroid autoimmunity. A regular screening for other antibodies is recommended in LADA patients according to GADA titer and gender.

Contribution of antibodies against IA-2β and zinc transporter 8 to classification of diabetes diagnosed under 40 years of age

OBJECTIVE

We investigated whether measuring autoantibodies against zinc transporter 8 (ZnT8A) and IA-2β (IA-2βA) may improve classification of new-onset type 1 diabetic patients based on detection of autoantibodies against insulin (IAA), GAD (GADA), and IA-2 (IA-2A). In addition, we studied the correlation of IA-2βA and ZnT8A with other biological and demographic variables.

RESEARCH DESIGN AND METHODS

Circulating autoantibodies were determined by liquid-phase radiobinding assays from 761 healthy control subjects and 655 new-onset (<1 week insulin) diabetic patients (aged 0-39 years) with clinical type 1 diabetes phenotype consecutively recruited by the Belgian Diabetes Registry.

RESULTS

At diagnosis, IA-2βA and ZnT8A prevalences were 41 and 58%, respectively. In IAA-negative, GADA-negative, and IA-2A-negative patients, one IA-2βA-positive and eleven ZnT8A-positive individuals were identified at the expense of eight and seven additional positive control subjects (1%), respectively, for each test. ZnT8A or IA-2βA screening increased (P < 0.001; McNemar) the number of patients with ≥2 antibodies both under (from 78 to 87% for ZnT8A and 82% for IA-2βA) and above age 15 (from 51 to 63% for ZnT8A and 56% for IA-2βA) versus 0% in control subjects. IA-2βA and ZnT8A were preferentially associated with IA-2A, and with younger age at diagnosis. Unlike ZnT8A, IA-2βA levels were positively correlated with HLA-DQ8 and negatively with HLA-DQ2. ZnT8A could replace IAA for classification of patients above age 10 without loss of sensitivity or specificity.

CONCLUSIONS

ZnT8A, and to a lesser degree IA-2βA, may usefully complement GADA, IA-2A, and IAA for classifying insulin-treated diabetes under age 40 years.

Autoimmune markers in diabetes

BACKGROUND

Type 1 diabetes (T1DM) results from cell-mediated autoimmune destruction of the β cells of the islets of Langerhans. Autoantibodies directed against the islets are useful clinical tools that allow the recognition and confirmation of β-cell autoimmunity.

CONTENT

In this review we define the term "islet autoantibody," describe the pathogenesis of autoantibody generation, and explain the uses of islet autoantibodies in clinical medicine and in research studies that concern the interruption or prevention of T1DM. We also discuss the biology of islet autoantibodies and their rates of appearance at the time of onset of T1DM and their appearance before the development of T1DM.

SUMMARY

The presence of islet autoantibodies in persons with diabetes confirms an autoimmune etiology. In nondiabetic individuals, islet autoantibodies are strong predictors of the later development of T1DM.

Autoimmunity predominates in a large South African cohort with Addison's disease of mainly European descent despite long-standing disease and is associated with HLA DQB*0201

OBJECTIVE

We sought to determine whether autoimmunity is the predominant cause of Addison's disease in South Africa and whether human leucocyte antigen (HLA) DQ association exists.

DESIGN

We compiled a national registry of patients from primary care, referral centres and private practices.

PATIENTS

A total of 144 patients, 94 of European descent, 34 Mixed Ancestry, 5 Asian and 11 Black Africans (mean age 45.9 years, range 2.7-88 years; mean duration of disease 13.1 years, range 0-50 years) and controls were matched for gender and ethnicity. All potential causes were investigated.

RESULTS

Fifty one per cent of cases (74 patients) were autoimmune in aetiology. Either 21-hydroxylase autoantibodies (72 patients, 50% of entire patient group) or adrenocortical autoantibodies (35 patients, 24%) were present, while 23% of patients had both. None of the Asian (n = 5) or Black (n = 11) patients had evidence of autoimmune disease. Overall 8% of patients had tuberculosis, 4% adrenoleucodystrophy, 1% adrenocorticotrophic hormone resistance syndrome and 6% X-linked adrenal hypoplasia. In those with autoimmune disease primary hypothyroidism (47%), premature ovarian failure (8%) and type 1 diabetes (7%) were the most prevalent accompanying autoimmune conditions. HLA DQB1*0201 alleles predominated in the autoimmune group (DQB1*0201: 65%vs 43% of controls P = 0.017) with the *0201/*0302 heterozygous genotype being the most prevalent (28%vs 8%P = 0.02).

CONCLUSIONS

While autoimmunity accounts for at least half of patients with Addison's disease in South Africa and is associated with HLA DQB1*0201, none of the Black Africans or Asians in this cohort had adrenal autoantibodies. Moreover, 21-hydroxylase autoantibodies were detectable in a higher proportion than adrenocortical autoantibodies, especially in those patients with a long history after disease onset.

An indirect competitive immunoassay for insulin autoantibodies based on surface plasmon resonance

We have developed a sensitive and specific method based on surface plasmon resonance (SPR) for detection of insulin autoantibodies (IAA) in serum samples from individuals at high risk of developing type 1 diabetes (T1D). When measuring trace molecules in undiluted sera with label-free techniques like SPR, non-specific adsorption of matrix proteins to the sensor surface is often a problem, since it causes a signal that masks the analyte response. The developed method is an indirect competitive immunoassay designed to overcome these problems. Today, IAA is mainly measured in radio immunoassays (RIAs), which are time consuming and require radioactively labeled antigen. With our SPR-based immunoassay the overall assay time is reduced by a factor of >100 (4 days to 50min), while sensitivity is maintained at a level comparable to that offered by RIA.

The islet autoantibody titres: their clinical relevance in latent autoimmune diabetes in adults (LADA) and the classification of diabetes mellitus

Latent autoimmune diabetes in the adult (LADA) is a slowly progressive form of autoimmune diabetes, characterized by diabetes-associated autoantibody positivity. A recent hypothesis proposes that LADA consists of a heterogeneous population, wherein several subgroups can be identified based on their autoimmune status. A systematic review of the literature was carried out to appraise whether the clinical characteristics of LADA patients correlate with the titre and numbers of diabetes-associated autoantibodies. We found that the simultaneous presence of multiple autoantibodies and/or a high-titre anti-glutamic acid decarboxylase (GAD)--compared with single and low-titre autoantibody--is associated with an early age of onset, low fasting C-peptide values as a marker of reduced pancreatic B-cell function, a high predictive value for future insulin requirement, the presence of other autoimmune disorders, a low prevalence of markers of the metabolic syndrome including high body mass index, hypertension and dyslipidaemia, and a high prevalence of the genotype known to increase the risk of Type 1 diabetes. We propose a more continuous classification of diabetes mellitus, based on the finding that the clinical characteristics gradually change from classic Type 1 diabetes to LADA and finally to Type 2 diabetes. Future studies should focus on determining optimal cut-off points of anti-GAD for differentiating clinically relevant diabetes mellitus subgroups.

Seasonality of month of birth differs between type 1 diabetes patients with pronounced beta-cell autoimmunity and individuals with lesser or no beta-cell autoimmunity

OBJECTIVE

To establish whether children with type 1 diabetes mellitus (T1D) with signs of pronounced beta-cell-specific autoimmunity as reflected by high autoantibody titers or positivity for several beta-cell-specific autoantibodies show a different pattern of month of birth (MOB) compared with children with T1D and low beta-cell autoimmunity and that of the general population.

RESEARCH DESIGN AND METHODS

Cosinor analysis was used to analyze MOB rhythmicity in Swedish children with new onset T1D (n = 572), in whom the glutamate decarboxylase autoantibody (GAD65Ab) titer was determined and compared with that in 833 healthy children, and in 505 children with T1D in Berlin, in whom the titers of autoantibodies to insulin, GAD65, and islet antigen-2 were compared with the MOB pattern in the general population (n = 446 571).

RESULTS

In both cohorts of children with T1D, we found that children with either a high GAD65Ab titer (above the 80th percentile) or positivity for three beta-cell-specific autoantibodies differed in their pattern of MOB from the healthy population.

CONCLUSIONS

Our past and present observations support the hypothesis that the autoimmune process leading to childhood T1D is in part triggered in the perinatal period by viral infections in genetically susceptible individuals. The present study suggests that the process is linked to titer levels of autoantibodies.

Assessing the utility of SELDI-TOF and model averaging for serum proteomic biomarker discovery

The SELDI-TOF technique was used to profile serum proteins from Type 1 diabetes (T1D) patients and healthy autoantibody-negative (AbN) controls. Univariate and multivariate analyses were performed to identify putative biomarkers for T1D and to assess the reproducibility of the SELDI technique. We found 146 protein/peptide peaks (581 total peaks discovered) in human serum showing statistical differences in expression levels between T1D patients and controls, with 84% of these peaks showing technical replication. Because individual proteins did not offer great power for disease prediction, we used our model averaging approach that combines the information from multiple multivariate models to accurately classify T1D and control subjects (88.9% specificity and 90.0% sensitivity). Analyses of a test subset of the data showed less accuracy (82.8% specificity and 76.2% sensitivity), although the results are still positive. Unfortunately, no multivariate model could be replicated using the same samples. This first attempt of high throughput analyses of the human serum proteome in T1D patients suggests that model averaging is a viable method for developing biomarkers; however, the reproducibility of SELDI-TOF is currently not sufficient to be used for classification of complex diseases like T1D.

A screening system for detecting genetic risk markers of type 1 diabetes in dried blood spots

BACKGROUND

Certain alleles among the genes that code for the human leukocyte antigens (HLA) confer susceptibility or resistance to the development of autoimmunity that causes type 1 diabetes (T1D). A number of ongoing diabetes research studies analyze dried blood spots (DBS) from newborn infants for HLA-D alleles to identify higher-risk children as early as possible. A commercially available assay to detect such alleles has recently become available using a dissociation- enhanced lanthanide fluorescence system found in many newborn screening laboratories.

METHODS

We adapted the system for use with DBS and improved the sample set-up for greater efficiency. We also developed an independent system for data analysis based on a spreadsheet program. These modifications were applied to HLA-DQB1 gene locus (DQB) analysis of 117 newborn DBS, and the results we obtained were compared with independent reference values.

RESULTS

Our assay modifications and independent data analysis improved sample throughput and result tabulation. DQB results from the modified assay were consistent with the reference values in all but one sample, which showed a partial match.

CONCLUSIONS

The modifications described here make this commercially available assay more suitable for high-throughput applications such as newborn screening. Our results show that this system allows highly accurate detection of DQB alleles that influence T1D risk.

The stages of type 1A diabetes

We can now predict the development of type 1 diabetes in man because it is a chronic autoimmune disorder with defined stages of disease. We can also readily prevent the disorder in animal models. A major goal is safe prevention in man, and for this we will almost certainly need a better understanding of pathogenesis, coupled with rigorous clinical trials.

What type of diabetes do young people have?

Although type 1 diabetes remains the most common type of diabetes in the pediatric population, there has been a dramatic rise in type 2 diabetes in youth. Clinical distinctions between these two major types have become blurred. As genetic and biochemical measures become more affordable and available, practical applications of these measures to better understand diabetes type in youth and the implications of diabetes type on the evolution of the disease are needed.

Autoimmune diagnostics in diabetes mellitus

Type 1 diabetes results from a specific destruction of the insulin-producing β-cells of the pancreas. The disease is characterized by the appearance of specific autoantibodies against islet cell antigens. Autoantibodies to insulin, glutamic acid decarboxylase, tyrosine phosphatase IA-2 and cytoplasmic islet cell antibodies are useful markers for the differential diagnosis of type 1 diabetes when clinical and metabolic criteria alone do not allow definite classification. Autoimmune diagnostics is of particular importance in adults to discriminate between type 1 and type 2 diabetes and to assess the diagnosis of latent autoimmune diabetes in adults.

Autoantibodies in diabetes

Islet cell autoantibodies are strongly associated with the development of type 1 diabetes. The appearance of autoantibodies to one or several of the autoantigens-GAD65, IA-2, or insulin-signals an autoimmune pathogenesis of beta-cell killing. A beta-cell attack may be best reflected by the emergence of autoantibodies dependent on the genotype risk factors, isotype, and subtype of the autoantibodies as well as their epitope specificity. It is speculated that progression to beta-cell loss and clinical onset of type 1 diabetes is reflected in a developing pattern of epitope-specific autoantibodies. Although the appearance of autoantibodies does not follow a distinct pattern, the presence of multiple autoantibodies has the highest positive predictive value for type 1 diabetes. In the absence of reliable T-cell tests, dissection of autoantibody responses in subjects of genetic risk should prove useful in identifying triggers of islet autoimmunity by examining seroconversion and maturation of the autoantibody response that may mark time to onset of type 1 diabetes. The complexity of the disease process is exemplified by multiple clinical phenotypes, including autoimmune diabetes masquerading as type 2 diabetes in youth and adults. Autoantibodies may also provide prognostic information in clinically heterogeneous patient populations when examined longitudinally.

Differential regulation of islet-specific glucose-6-phosphatase catalytic subunit-related protein gene transcription by Pax-6 and Pdx-1

Islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) is selectively expressed in islet beta cells and is a major autoantigen in a mouse model of type I diabetes. The analysis of IGRP-chloramphenicol acetyltransferase (CAT) fusion gene expression through transient transfection of islet-derived betaTC-3 cells revealed that a promoter region, located between -273 and -254, is essential for high IGRP-CAT fusion gene expression. The sequence of this promoter region does not match that for any known islet-enriched transcription factor. However, data derived from gel retardation assays, a modified ligation-mediated polymerase chain reaction in situ footprinting technique and a SDS-polyacrylamide separation/renaturation procedure led to the hypothesis that this protein might be Pax-6, a conclusion that was confirmed by gel supershift assays. Additional experiments revealed a second non-consensus Pax-6 binding site in the -306/-274 IGRP promoter region. Pax-6 binding to these elements is unusual in that it appears to require both its homeo and paired domains. Interestingly, loss of Pax-6 binding to the -273/ -246 element is compensated by Pax-6 binding to the -306/-274 element and vice versa. Gel retardation assays revealed that another islet-enriched transcription factor, namely Pdx-1, binds four non-consensus elements in the IGRP promoter. However, mutation of these elements has little effect on IGRP fusion gene expression. Although chromatin immunoprecipitation assays show that both Pax-6 and Pdx-1 bind to the IGRP promoter within intact cells, in contrast to the critical role of these factors in beta cell-specific insulin gene expression, IGRP gene transcription appears to require Pax-6 but not Pdx-1.