Massimo Pietropaolo

Prediction of Type I Diabetes in First-Degree Relatives Using a Combination of Insulin, GAD, and ICA512bdc/IA-2 Autoantibodies

Islet cell antibodies (ICAs) are predictive of type I diabetes in first-degree relatives, but this immunohistochemical assay has proven difficult to standardize. As an alternative, we assessed the use of radioassays for antibodies against three molecularly characterized islet autoantigens, including ICA512bdc (amino acid residues 256–979 of the IA-2 molecule, incorporating the intracellular domain). We measured insulin autoantibodies (IAAs), GAD autoantibodies (GAAs), and ICA512bdc autoantibodies (ICA512bdcAAs) by radioassay, in addition to ICAs, in 882 first-degree relatives of patients with type I diabetes, 50 of whom later developed diabetes with a median follow-up of 2.0 years (maximum 11.3 years). The cutoff for each radioassay was determined by testing >200 control subjects. When autoantibody frequencies among the relatives were analyzed according to relationship to the proband, the offspring of diabetic fathers had a higher frequency of ICA512bdcAAs (P = 0.008), IAAs (P = 0.0001) and GAAs (P = 0.0001) than the offspring of diabetic mothers. ICA512bdcAAs and IAAs both showed a significant association with HLA-DR4-DQ8 (P = 0.0005). Among relatives developing diabetes, 98% had one or more of IAAs, GAAs, or ICA512bdcAAs, and 80% had two or more of these autoantibodies, compared with none of the control subjects. Using survival analysis to allow for different lengths of follow-up, there was a significant increase in the risk of diabetes with the number of these autoantibodies present, comparing zero, one, two, and three autoantibodies (P < 0.0001, log-rank test), and by Cox regression analysis, this was independent of ICAs and age. For relatives with two or more of these autoantibodies, the risk of diabetes within 3 years was 39% (95% CI, 27–52) and the risk within 5 years was 68% (95% CI, 52–84). Relatives with all three autoantibodies had a risk within 5 years estimated to be 100%. The presence of low first-phase insulin release further increased the risk for relatives with one or two autoantibodies. We conclude that the presence of two or more autoantibodies (out of IAAs, GAAs, and ICA512bdcAAs) is highly predictive of the development of type I diabetes among relatives.

The emerging role of autophagy in the pathophysiology of diabetes mellitus

An emerging body of evidence supports a role for autophagy in the pathophysiology of type 1 and type 2 diabetes mellitus. Persistent high concentrations of glucose lead to imbalances in the antioxidant capacity within the cell resulting in oxidative stress-mediated injury in both disorders. An anticipated consequence of impaired autophagy is the accumulation of dysfunctional organelles such as mitochondria within the cell. Mitochondria are the primary site of the production of reactive oxygen species (ROS), and an imbalance in ROS production relative to the cytoprotective action of autophagy may lead to the accumulation of ROS. Impaired mitochondrial function associated with increased ROS levels have been proposed as mechanisms contributing to insulin resistance. In this article we review and interpret the literature that implicates a role for autophagy in the pathophysiology of type 1 and type 2 diabetes mellitus as it applies to β-cell dysfunction, and more broadly to organ systems involved in complications of diabetes including the cardiovascular, renal and nervous systems.

ICA512 Autoantibody Radioassay

As part of a general program of screening islet expression libraries we have identified a clone from a λgt11 human islet expression library that reacts with human diabetic sera and, upon sequencing, was determined to be the neuroendocrine islet autoantigen ICA512 (islet cell antigen 512). In the current communication, we describe the development of a radioassay for autoantibodies to ICA-512 (ICA512AA) using in vitro transcribed and translated protein for production of labeled antigen. Our initial results indicate that this radioassay is significantly more sensitive than the enzyme-linked immunosorbant assay, which uses a COOH-terminal fragment of ICA512. The ICA512AA radioassay uses a 96-well format with membrane separation of antibody bound from free antigen and should be readily adaptable to automated large-scale screening. Only 7 μl of serum is required for triplicate determinations. In order to determine the specificity and sensitivity of this assay and estimate its positive predictive value, we have studied 42 new-onset diabetic patients, 33 first-degree relatives of diabetic patients followed to diabetes, 694 islet cell antibody-negative (ICA–) relatives, and 205 normal control subjects. Thirty-eight percent of new-onset patients and 48% of relatives followed to diabetes express autoantibodies to ICA512 exceeding the 99th percentile of the normal control subjects. In contrast, only 1.4% of ICA– first-degree relatives were positive for ICA512 autoantibodies. By using three radioassays for islet autoantibodies against insulin, glutamic acid decarboxylase 65 (GAD65), and ICA512, 100% of the prediabetic sera we have studied have been shown to express antibodies to at least one antigen, and the majority (88%, 27 of 31) express two or more. ICA512 autoantibodies provide a specific marker for type I diabetes and, in combination with antibodies to GAD65 and insulin, should facilitate the prediction of type I diabetes.

How Does Type 1 Diabetes Develop?: The Notion of Homicide or β-Cell Suicide Revisited

Despite decades of acknowledging that a loss of insulin-producing pancreatic β-cells is central to the disorder now referred to as type 1 diabetes, the specific roles for genetic susceptibility, environmental factors, the immune system, and β-cells themselves in the pathogenic processes underlying the disorder remain unclear (1,2). Looking back over this period, one can identify a handful of conceptualizations that were seminal in their attempt to address this issue, including that posited by Dr. Gian Franco Bottazzo in his 1986 article, “Death of a Beta Cell: Homicide or Suicide?” (3). Bottazzo questioned whether the disorder’s pathogenesis weighed more heavily (or exclusively) on processes related to immune responsiveness (i.e., homicide) or the fragility of β-cells leading to self-destruction (i.e., suicide). Many reasons exist with respect to why we are in this knowledge void, including the exceedingly complex nature of type 1 diabetes, the likelihood that this disorder may represent a disease with more than one etiology, as well as the complex interplay of genetics, the immune system, and the environment. One limitation in solving important pathogenic questions in type 1 diabetes has likely been suboptimal cross-talk among geneticists, epidemiologists, endocrinologists, and others. Our own approach to overcoming this limitation has been to try to increase collaboration between cell biologists and immunologists as a critical step in closing knowledge gaps regarding the disorder’s pathogenesis. The opinion put forward within this Perspectives article by this group of authors is one where multiple and clearly unique properties of the β-cell appear fundamental to the loss of immune tolerance, accompanied by immune-mediated destruction. The Bottazzo article (3) was unique in its form of presentation, in that the prose represented the equivalent workings of a legal stenographer recording the debate between two counsels: one for the prosecution (i.e., β-cell homicide) the other representing the …

Late progression to diabetes and evidence for chronic beta-cell autoimmunity in identical twins of patients with type I diabetes.

Previous studies suggest that after 6 years of discordance, identical twin pairs rarely become concordant for type I diabetes. With up to 39 years of follow-up from the onset of diabetes in the index twin, we determined how many discordant twins have evidence of β-cell autoimmunity and how many develop overt diabetes. We longitudinally followed 23 pairs of identical twins (or triplets) that were selected from a total group of 30 pairs because they were discordant for type I diabetes when first ascertained. Seven developed diabetes after 3, 3, 7, 8, 9, 31 and 36 years of discordance. By survival analysis, the concordance after 10 years from the onset of diabetes in the index twin was estimated as 23% (95% confidence interval, 5–40%), increasing to 38% (95% confidence interval, 8–69%) after 31 years. Among 16 twins remaining nondiabetic at last follow-up (8–39 years of discordance), 12 were assessed with serial intravenous glucose tolerance tests and a total of 407 measurements by radioassay of antibodies against three defined autoantigens (glutamic acid decarboxylase, insulin, and the recently cloned molecule ICA512). Two-thirds (8 of 12) had evidence of β-cell autoimmunity (persistently positive autoantibody levels) and/or first-phase insulin release < the 1st percentile of control subjects. In summary, identical twins may develop diabetes after a prolonged period of discordance and ∼ two-thirds of long-term discordant twins have evidence of persistent β-cell autoimmunity and/or β-cell damage. The concordance for β-cell autoimmunity, therefore, is much higher than for overt diabetes. This suggests that additional environmental or non-Mendelian genetic factors or time are required for the development of type I diabetes.

Estimating the cost of type 1 diabetes in the U.S.: a propensity score matching method.

Background Diabetes costs represent a large burden to both patients and the health care system. However, few studies that examine the economic consequences of diabetes have distinguished between the two major forms, type 1 and type 2 diabetes, despite differences in underlying pathologies. Combining the two diseases implies that there is no difference between the costs of type 1 and type 2 diabetes to a patient. In this study, we examine the costs of type 1 diabetes, which is often overlooked due to the larger population of type 2 patients, and compare them to the estimated costs of diabetes reported in the literature. Methodology/Principal Findings Using a nationally representative dataset, we estimate yearly and lifetime medical and indirect costs of type 1 diabetes by implementing a matching method to compare a patient with type 1 diabetes to a similar individual without the disease. We find that each year type 1 diabetes costs this country

The Heterogeneity of Diabetes: Unraveling a Dispute: Is Systemic Inflammation Related to Islet Autoimmunity?

14.4 billion (11.5–17.3) in medical costs and lost income. In terms of lost income, type 1 patients incur a disproportionate share of type 1 and type 2 costs. Further, if the disease were eliminated by therapeutic intervention, an estimated

Immunology and genetics of type 1 diabetes

10.6 billion (7.2–14.0) incurred by a new cohort and

Autoantibodies in Human Diabetes

422.9 billion (327.2–519.4) incurred by the existing number of type 1 diabetic patients over their lifetime would be avoided. Conclusions/Significance We find that the costs attributed to type 1 diabetes are disproportionately higher than the number of type 1 patients compared with type 2 patients, suggesting that combining the two diseases when estimating costs is not appropriate. This study and another recent contribution provides a necessary first step in estimating the substantial costs of type 1 diabetes on the U.S.

Islet Autoantigens: Structure, Function, Localization, and Regulation

Diabetes is an emblematic example of a heterogeneous disease. Systemic inflammation has emerged as a prominent factor in the type 2 diabetes pathoetiology, but it remains ill-defined in type 1 diabetes. There is a wide spectrum of associations between inflammatory responses and diabetic syndromes. At one end of this spectrum, there is type 1 diabetes for which there is convincing evidence that chronic inflammation of pancreatic islets is a central aspect of disease pathogenesis. At the opposite end, is type 2 diabetes that is clearly associated with systemic inflammation, which could be either the cause or simply mark the underlying pathology. Accumulating evidence has substantiated that a subgroup of adult patients clinically diagnosed with type 2 diabetes exhibit autoantibody responses to islet autoantigens. The presence of these immunologic abnormalities is associated with a severe insulin secretory defect and the absence of signs of systemic inflammation as documented by plasma C-reactive protein and fibrinogen levels that are comparable with those of control populations. Islet autoantibody evaluation should be part of the diagnostic assessment for clinically diagnosed type 2 diabetes not only because it might predict the rate of progression to insulin requirement in adult populations but also to identify a pathogenically distinct disease phenotype characterized by the absence of systemic inflammation and its related disorders. A more appropriate characterization of this subgroup of clinically diagnosed type 2 diabetes, diabetes of autoimmune pathogenesis, will promote future research into the etiology, natural history, and treatment.