Adiponectin is a better predictor of endothelial function of the coronary artery than HOMA-R, body mass index, immunoreactive insulin, or triglycerides

BACKGROUND

Previous studies have demonstrated that decreased levels of circulating adiponectin correlate with endothelial dysfunction in peripheral arteries. However, the relationship between adiponectin levels and endothelial function in coronary arteries remains unclear. The goal of the present study was to determine whether circulating adiponectin concentrations are a useful predictor of coronary endothelial function.

METHODS

Thirty-six consecutive non-diabetic patients with normal or mildly diseased coronary arteries were enrolled in this study. Coronary endothelial function was evaluated by coronary vascular response to acetylcholine (Ach). The relationship between coronary vasoreactivity and adiponectin or other biochemical or anthropometric parameters was investigated. The predictive value of adiponectin level for assessment of coronary endothelial dysfunction was assessed at the best cut-off point.

RESULTS

In a simple regression analysis, log-transformed adiponectin concentrations positively correlated with the percent change in coronary blood flow (CBF) and coronary artery diameter (CAD) induced by Ach (r=0.62, p<0.0001; r=0.63, p<0.0001, respectively). Insulin resistance index (HOMA-R), body mass index, immunoreactive insulin, and triglycerides concentrations also significantly correlated with the percent change in CBF and CAD. However, in a multiple regression analysis, log-transformed adiponectin concentration was the only independent predictor of the percent change in CBF and CAD (p<0.0001; p<0.0001, respectively). Furthermore, patients with adiponectin concentrations <6.3 mg/L demonstrated coronary endothelial dysfunction with high specificity both in terms of CBF and CAD response (85%; 88%, respectively).

CONCLUSIONS

Adiponectin is a better predictor of coronary endothelial function than other factors such as HOMA-R, body mass index, immunoreactive insulin, and triglycerides.

Diabetes therapy trials with inhaled insulin

Administration of insulin by inhalation was first attempted > 50 years ago. At that time, little was known concerning effective delivery systems and insulin formulations. The recent development of pulmonary delivery systems for the administration of insulin is driven by the reluctance of patients and their providers to initiate insulin earlier in the course of Type 2 diabetes, the desire to reduce the number of daily insulin injections for both Type 1 and 2 patients, and the recent emphasis on intensified glycaemic control including postprandial glycaemic control. The deep lung is a unique mucosal tissue having a surface area of > 100 m2 and is readily accessible both to the external environment and to drug delivery, provided that appropriate conditions are met. There have been four mid- to late-phase pulmonary insulin programmes using modern inhalation devices that will be reported in this paper. The programmes differ in the choice of delivery systems, the formulations of insulin and reported bioavailability, pharmacokinetic and glucodynamic profiles and adverse events. However, all systems successfully deliver insulin to the deep lung and biological effectiveness compares favourably with injected subcutaneous insulins.

Multiple germline kappa light chains generate anti-insulin B cells in nonobese diabetic mice

The highly selective nature of organ-specific autoimmune disease is consistent with a critical role for adaptive immune responses against specific autoantigens. In type 1 diabetes mellitus, autoantibodies to insulin are important markers of the disease process in humans and nonobese diabetic (NOD) mice; however, the Ag-specific receptors responsible for these autoantibodies are obscured by the polyclonal repertoire. NOD mice that harbor an anti-insulin transgene (Tg) (V(H)125Tg/NOD) circumvent this problem by generating a tractable population of insulin-binding B cells. The nucleotide structure and genetic origin of the endogenous kappa L chain (Vkappa or IgL) repertoire that pairs with the V(H)125Tg were analyzed. In contrast to oligoclonal expansion observed in systemic autoimmune disease models, insulin-binding B cells from V(H)125Tg/NOD mice use specific Vkappa genes that are clonally independent and germline encoded. When compared with homologous IgL genes from nonautoimmune strains, Vkappa genes from NOD mice are polymorphic. Analysis of the most frequently expressed Vkappa1 and Vkappa9 genes indicates these are shared with lupus-prone New Zealand Black/BINJ mice (e.g., Vkappa1-110*02 and 9-124) and suggests that NOD mice use the infrequent b haplotype. These findings show that a diverse repertoire of anti-insulin B cells is part of the autoimmune process in NOD mice and structural or regulatory elements within the kappa locus may be shared with a systemic autoimmune disease.

Uncoupling of anergy from developmental arrest in anti-insulin B cells supports the development of autoimmune diabetes

Loss of tolerance is considered to be an early event that is essential for the development of autoimmune disease. In contrast to this expectation, autoimmune (type 1) diabetes develops in NOD mice that harbor an anti-insulin Ig transgene (125Tg), even though anti-insulin B cells are tolerant. Tolerance is maintained in a similar manner in both normal C57BL/6 and autoimmune NOD mice, as evidenced by B cell anergy to stimulation through their Ag receptor (anti-IgM), TLR4 (LPS), and CD40 (anti-CD40). Unlike B cells in other models of tolerance, anergic 125Tg B cells are not arrested in development, and they enter mature subsets of follicular and marginal zone B cells. In addition, 125Tg B cells remain competent to increase CD86 expression in response to both T cell-dependent (anti-CD40) and T cell-independent (anti-IgM or LPS) signals. Thus, for anti-insulin B cells, tolerance is characterized by defective B cell proliferation uncoupled from signals that promote maturation and costimulator function. In diabetes-prone NOD mice, anti-insulin B cells in this novel state of tolerance provide the essential B cell contribution required for autoimmune beta cell destruction. These findings suggest that the degree of functional impairment, rather than an overt breach of tolerance, is a critical feature that governs B cell contribution to T cell-mediated autoimmune disease.

Early and quantal (by litter) expression of insulin autoantibodies in the nonobese diabetic mice predict early diabetes onset

Aiming to study the early stages of type 1 diabetes phenotype, before insulitis appears, we measured insulin autoantibodies (IAA) between 3 and 5 wk of age in the NOD mouse (early-IAA (E-IAA)). We report that IAA are found as early as at 3 wk of age, at weaning, and their expression is a quantal phenotype. Maternal autoantibody status influences this early phenotype, because animals of litters issued from IAA-positive ante partum mothers develop E-IAA with a significantly higher incidence than animals issued from IAA-negative mothers. These E-IAA represent synthesized rather than transplacental autoantibodies, as evidenced by higher levels in many offspring compared with maternal IAA, and negative as well as positive offspring in the same litters and it correlates with early diabetes onset, defining the first autoimmune window in diabetes pathogenesis. Therefore, autoimmune processes leading to type 1 diabetes initiate early in life, are influenced by maternal autoantibody status, and can be revealed by the presence of IAA. Our data suggest that the mechanisms responsible for the breakdown of self-tolerance are subjected not only to genetic predisposition, but also to the physiological status of the mother. Pathological progression to autoimmunity is marked by the presence of immunological windows relating early steps with final disease onset.

Maternal immunity to insulin does not affect diabetes risk in progeny of non obese diabetic mice

It has been suggested that maternal environment, in particular maternal autoantibodies, modify the risk of developing autoimmune diabetes in offspring. The aim of this study was to determine whether modification of maternal environment and maternal diabetes risk through immunization affects autoimmune diabetes risk in the progeny. The risk of developing insulin antibodies and of developing diabetes was determined in 113 female progeny of non obese diabetic (NOD) dams that were immunized with insulin, control antigen or vehicle before or during pregnancy. Although NOD dams immunized with insulin were rendered diabetes resistant (40% diabetes by age 36 weeks versus 100% in control dams), diabetes development in their female offspring (72%, 26/36) was similar to that in female offspring of dams immunized with glucagon (82%, 22/27) or vehicle (76%, 19/25). Furthermore, no significant differences in diabetes development or insulin autoantibody titres were observed between female progeny of insulin autoantibody positive NOD dams (82% diabetes by age 36 weeks, 18/22), insulin autoantibody negative NOD dams (75%, 41/55), and NOD dams that had antibodies against exogneous insulin (71%, 22/31). The findings suggest that modification of the maternal risk for autoimmune diabetes via antigen-specific immunization is not transferred to progeny and that fetal exposure to insulin autoantibodies does not increase the risk for diabetes development.

Dermal enhancement: bacterial products on intact skin induce and augment organ-specific autoimmune disease

The skin is both an essential barrier for host defense and an important organ of immunity. In this study, we show that the application of cholera toxin to intact mouse skin induces and enhances autoimmune diseases affecting organs at distant anatomic sites, whereas its administration by the mucosal route has been reported to have the opposite effect. First, the CNS autoantigen myelin oligodendrocyte glycoprotein 35-55, when applied repeatedly with cholera toxin to the intact skin of healthy C57BL/6 mice, induced relapsing paralysis with demyelinating immunopathologic features similar to multiple sclerosis. Second, the application of cholera toxin in the absence of autoantigen exacerbated the severity of conventional experimental autoimmune encephalomyelitis induced by myelin oligodendrocyte glycoprotein in CFA. Third, the application of cholera toxin to the intact skin of NOD/Lt mice, with or without insulin B peptide 9-23, exacerbated insulitis and T lymphocyte-derived IFN-gamma and IL-4 production in the islets of Langerhans, resulting in an increased incidence and rate of onset of autoimmune diabetes. The data presented in this study highlight the different outcomes of adjuvant administration by different routes. Because dermal application of cholera toxin, and other bacterial products with similar adjuvant activities, is being developed as a clinical vaccination strategy, these data raise the possibility that it could precipitate autoimmune disease in genetically susceptible humans.

Systemic overexpression of IL-10 induces CD4+CD25+ cell populations in vivo and ameliorates type 1 diabetes in nonobese diabetic mice in a dose-dependent fashion

Early systemic treatment of nonobese diabetic mice with high doses of recombinant adeno-associated virus (rAAV) vector expressing murine IL-10 prevents type 1 diabetes. To determine the therapeutic parameters and immunological mechanisms underlying this observation, female nonobese diabetic mice at 4, 8, and 12 wk of age were given a single i.m. injection of rAAV-murine IL-10 (10(4), 10(6), 10(8), and 10(9) infectious units (IU)), rAAV-vector expressing truncated murine IL-10 fragment (10(9) IU), or saline. Transduction with rAAV-IL-10 at 10(9) IU completely prevented diabetes in all animals injected at all time points, including, surprisingly, 12-wk-old animals. Treatment with 10(8) IU provided no protection in the 12-wk-old injected mice, partial prevention in 8-wk-old mice, and full protection in all animals injected at 4 wk of age. All other treatment groups developed diabetes at a similar rate. The rAAV-IL-10 therapy attenuated pancreatic insulitis, decreased MHC II expression on CD11b+ cells, increased the population of CD11b+ cells, and modulated insulin autoantibody production. Interestingly, rAAV-IL-10 therapy dramatically increased the percentage of CD4+CD25+ regulatory T cells. Adoptive transfer studies suggest that rAAV-IL-10 treatment alters the capacity of splenocytes to impart type 1 diabetes in recipient animals. This study indicates the potential for immunomodulatory gene therapy to prevent autoimmune diseases, including type 1 diabetes, and implicates IL-10 as a molecule capable of increasing the percentages of regulatory cells in vivo.

Immune responses to insulin aspart and biphasic insulin aspart in people with type 1 and type 2 diabetes

OBJECTIVE

The antibody responses to a novel rapid-acting insulin analog, insulin aspart (IAsp), and their potential clinical correlates were studied with a specifically developed method in 2,420 people with diabetes treated for up to 1 year with preprandial subcutaneous injections of IAsp.

RESEARCH DESIGN AND METHODS

Circulating insulin antibodies were analyzed by radioimmunoassay with (125)I insulin or IAsp tracers and polyethylene glycol precipitation. Four multinational, open, parallel group studies were conducted in Europe and North America, with a total of 1,534 people with diabetes exposed to IAsp and 886 people exposed to human insulin (HI) as meal-related insulin for 6-12 months.

RESULTS

Insulin antibodies specific to HI or IAsp were absent in a majority of patients throughout the 6- to 12-month study periods. A majority of the patients (64-68%) had antibodies cross-reacting between HI and IAsp when entering the studies, with baseline levels (means +/- SD of percent bound/total) of 16.6 +/- 16.3% in study 1 and 10.3 +/- 14.0% in study 4. In all four studies, cross-reactive antibodies increased in patients exposed to IAsp, with a maximum at 3 months, and thereafter there was a decline toward baseline levels at 9-12 months (levels at 3 and 12 months: 22.3 +/- 19.7 and 16.8 +/- 16.5% in study 1 and 21.5 +/- 21.9 and 16.9 +/- 17.4% in study 4). Antibody levels showed similar changes in people with type 1 and type 2 diabetes, and there was no consistent relationship between antibody formation and glycemic control or between antibody formation and safety in terms of adverse events.

CONCLUSIONS

Treatment with IAsp is associated with an increase in cross-reactive insulin antibodies, with a subsequent fall toward baseline values, without any indication of clinical relevance because no effect on efficacy or safety could be identified.

Transient insulin autoantibody expression independent of development of diabetes: comparison of NOD and NOR strains

NOD mice spontaneously develop anti-insulin autoantibodies associated with the subsequent development of diabetes. NOD mice that express insulin autoantibodies at 8 weeks of age have a diabetes risk exceeding 90%, while mice that do not express autoantibodies by 16 weeks have a risk of less than 20%. NOD female mice expressed insulin autoantibodies more often than male mice (13/15+ vs. 6/15+). Autoantibodies characteristically developed between 8 and 20 weeks and then for most mice became negative at diabetes onset in NOD mice. In the diabetes-free strain NOR mice, spontaneous expression of insulin autoantibodies was observed in less mice (female 8/15+, male 3/10+) compared to NOD mice. The expression of autoantibodies was transient in NOR mice and followed the same time-course as for NOD mice and they were all negative by 28 weeks (without progression to diabetes). No correlation was found in NOR mice between the levels of autoantibodies and insulitis. The program of insulin autoantibody expression is regulated over approximately 5 months for both NOD and NOR mice with only NOD mice developing diabetes, indicating that depending upon genetic combination, the presence of insulin autoantibodies does not always predict diabetes development. In addition, this data is not consistent with the hypothesis that the time-course of autoantibodies simply reflects the destruction of beta-cells with development of diabetes.

Insulin binds to glucagon forming a complex that is hyper-antigenic and inducing complementary antibodies having an idiotype-antiidiotype relationship

We demonstrate using physico-chemical techniques that insulin binds to glucagon with a Kd of 0.89 micromolar. While such binding is of little significance physiologically, it has important immunological consequences. Hormone binding is mirrored by specific binding between insulin antibody and glucagon antibody to form idiotype-antiidiotype complexes observable by Ouchterlony immunodiffusion and ELISA. These complexes may provide new insights into the formation of circulating immune complexes in diabetes. The insulin-glucagon complex is hyper-antigenic, inducing antibody production at concentrations that do not elicit immune responses from the individual hormones. The resulting immune response is not primarily against the individual hormones, but against the complex. In fact, all so-called insulin antibodies tested (rabbit, guinea pig, mouse and human) show substantially higher affinity for insulin-glucagon complex than for insulin alone, suggesting that this complex is the primary antigen in most, if not all, cases. These results lead to several testable predictions, including the possibility that glucagon antibody will bind to insulin receptors to cause type 2 (antibody mediated) insulin resistance.

Intermolecular antigen spreading occurs during the preclinical period of human type 1 diabetes

Intra- and intermolecular spreading of T cell responses to autoantigens has been implicated in the pathogenesis of autoimmune diseases. Therefore, we questioned whether T cell responses from subjects identified as at-risk (positive for autoantibody reactivity to islet proteins) for the development of type 1 diabetes, a cell-mediated autoimmune disease, would demonstrate intermolecular Ag spreading of T cell responses to islet cell proteins. Previously, we have demonstrated that by the time subjects develop type 1 diabetes, they have T cell responses to numerous islet proteins, whereas T cells from normal controls respond to a limited number of islet proteins. Initial testing of PBMC responses from 25 nondiabetic at-risk subjects demonstrated that 16 of the 25 subjects have PBMC responses to islet proteins similar to controls. Fourteen of these 16 subjects were available for follow-up. Eleven of the 14 developed T cell responses to increasing numbers of islet proteins, and 6 of these subjects developed type 1 diabetes. In the nine subjects who already demonstrated T cell Ag spreading at the initial visit, four were available for follow-up. Of these four, two had increases in T cell reactivity to islet proteins, while two maintained their initial levels of T cell reactivity. We also observed Ag spreading in autoantibody reactivity to islet proteins in nine of the 18 at-risk subjects available for follow-up. Our data strongly support the conclusion that intermolecular spreading of T cell and Ab responses to islet proteins occurs during the preclinical period of type 1 diabetes.

Insulin antibody response to bovine insulin therapy: functional significance among insulin requiring young diabetics in India

The majority of young diabetics in India prefer to use low-cost bovine insulin for economic reasons. Therefore, the question of insulin antibody response to bovine insulin and its functional significance is still relevant in the Indian context. We assessed insulin antibody response in 52 young diabetics (type 1, n=25, malnutrition modulated form of diabetes, n=19 and fibrocalculous pancreatopathy (FCP) n=8) on bovine insulin therapy (mean duration 3.0+/-2.1 years) using an internationally standardised in-house radioligand assay. The functional significance of insulin antibody was assessed by calculating their affinity constant, maximum binding capacity and total insulin binding power by Scatchard analysis (type 1, n=14, malnutrition modulated form of diabetes, n=11). All the patients treated with bovine insulin showed high titers of insulin antibodies with S.D. score ranging from 5.1 to 42.0. No significant difference was observed in the mean S.D. score of insulin antibodies in the three diabetic groups. The mean daily insulin dose, maximum insulin binding capacity and total insulin binding power were significantly higher in type 1 when compared to the malnutrition modulated form of diabetes (36+/-8 vs. 26+/-11 IU/day, P<0.05; 9. 7+/-7.8 vs. 4.0+/-3.9 nmol/l, P=0.03 and 59+/-29 vs. 29+/-43, P=0.01, respectively). Insulin antibodies S.D. score and its affinity did not show significant relationship with daily insulin dose and glycemic control (HbAl) at admission. Only 24+/-7% variations in daily insulin requirement were accounted for by total insulin binding power. There was a significant inverse relationship between insulin antibody S.D. score and duration of insulin therapy (r=-0. 4172, P<0.0004). To conclude, insulin antibody response following bovine insulin therapy is not different among type 1, malnutrition modulated form of diabetes and FCP diabetes. The insulin antibody response to bovine insulin therapy does not contribute significantly to increase in daily insulin requirement in bovine insulin treated insulin requiring young diabetics.

Insulin antibody response to a short course of human insulin therapy in women with gestational diabetes

OBJECTIVE

To assess the insulin antibody (IA) response to human insulin (HI) therapy in women with gestational diabetes.

RESEARCH DESIGN AND METHODS

IAs were measured by a competitive radiobinding assay in 50 women with gestational diabetes before and during treatment with HI and after delivery. At delivery, 15 maternal-cord blood sample pairs were analyzed for IA. As a reference, we searched for IA in 25 new-onset type I diabetic patients, before and at 3, 6, and 12 months after insulin therapy.

RESULTS

Insulin autoantibodies (IAAs) were detected in 1 of 50 women with gestational diabetes and 4 of 16 type I diabetic patients (P < 0.05). At the end of pregnancy after 9.3 +/- 6.8 weeks on insulin therapy, 22 of 50 (44%) women with gestational diabetes became IA+ and 4 additional women were found to be positive 2 months postpartum. After 3 months on insulin, type I diabetic patients showed a higher rate of IA positivity (92%, P < 0.001). IA titers at the end of pregnancy were associated with the cumulative insulin dose (r = 0.29, P < 0.05). Postpartum, IA disappeared slowly in most IA+ women, but two women still showed IA 2 years after delivery Titers in cord blood were strongly related to those in maternal blood (r = 0.74, P < 0.01). The rate of adverse fetal outcome did not differ in IA and IA- mothers (27 vs. 40%, NS).

CONCLUSIONS

HI is immunogenic, and a short course of HI therapy induces IA in approximately 50% of women with gestational diabetes and 92% of type I diabetic patients. In women with gestational diabetes, insulin dose is slightly associated with IA titers. These IAs apparently cross the placenta. Fetal outcome does not differ according to the maternal IA status, and IAs disappear gradually after delivery but may remain positive for 2 years after delivery.

Immunization therapies in the prevention of diabetes

Insulin-dependent diabetes (IDD), being an autoimmune disease, offers several opportunities for immunological interventions that may result either in the reduction of disease severity or in delaying diabetes onset. Among the various experimental preventative approaches, parenteral immunization with islet-specific autoantigens appears to be practically simpler and promising. We have previously shown that immunization with insulin, insulin B chain and B chain epitope (p9-23), but not insulin A chain, in incomplete Freund's adjuvant (IFA) and in alum (with B chain) delayed/prevented diabetes onset in NOD mice. Here we demonstrate the protective efficacy of affinity purified GAD65 in IFA. While both insulin B chain and GAD65 significantly delayed the onset of diabetes (P=0.001), a recently described tyrosine phosphatase (IA-2) antigen did not (P=0.38). Interestingly, B chain immunization reduced the incidence of cyclophosphamide (CY)-accelerated diabetes by about 50-55%. We also provide further evidence that B chain, upon increased adsorption to alum, could improve on its protective capacity in NOD mice.

Interferon-alpha therapy may induce insulin autoantibody development in patients with chronic viral hepatitis

Development of type 1 insulin-dependent diabetes mellitus has been recently reported in patients who underwent interferon-alpha (IFN-alpha) therapy because of chronic viral hepatitis. Furthermore IFN-alpha seems to be involved in the immunological events that lead to beta-cell destruction and development of type 1 diabetes. To evaluate whether IFN-alpha treatment could elicit an autoimmune response against beta-cell antigens, we determined the occurrence of islet cell antibodies and insulin autoantibodies in the sera of 60 patients with HCV- or HBV-related chronic hepatitis who had been treated with IFN-alpha for 6 or 12 months. The presence of antibodies against thyroglobulin, thyroid microsomal antigen, gastric parietal cells, and non-organ-specific antigens was also investigated. Insulin autoantibody positivity was observed in 2/60 (3.3%), 8/60 (13.3%), and 4/30 (13.3%) patients, before IFN-alpha treatment, and after 6 months and 12 months of therapy, respectively. None of the studied patients developed islet cell antibodies or type 1 diabetes. Before IFN-alpha therapy four patients showed thyroid autoantibodies and four others developed antibodies against thyroglobulin and/or thyroid microsomal antigen during the treatment. Coexistence of insulin autoantibodies and thyroid autoantibodies was observed in only two patients. Our results showed that IFN-alpha therapy in patients with chronic viral hepatitis is capable of inducing development of autoantibodies against insulin. This event seems to be not related to other autoimmune disorders.

Perinatal autoimmunity in offspring of diabetic parents. The German Multicenter BABY-DIAB study: detection of humoral immune responses to islet antigens in early childhood

IDDM results from immune-mediated destruction of insulin-producing pancreatic beta-cells in individuals genetically susceptible for the disease. There is evidence that the 65-kDa isoform of GAD plays a critical role in the induction of autoimmune diabetes in NOD mice. In humans, it is still unclear when and to what beta-cell antigens autoreactive lymphocytes become activated during early disease. We conducted a prospective study from birth, BABY-DIAB, among children of mothers with IDDM or gestational diabetes or fathers with IDDM, and we investigated the temporal sequence of antibody responses to islet cells (ICA), insulin (IAA), GAD (GADA), and the protein tyrosine phosphatase IA-2/ICA512 (IA-2A). Of 1,019 children included at birth, we have currently followed 513 to the age of 9 months, 214 to the age of 2 years, and 37 to the age of 5 years. At birth, all antibody specificities were frequent in newborns of diabetic mothers but not fathers and are suggested to be transplacentally acquired because they are strongly correlated with antibody levels in their diabetic mothers. In early childhood, antibody levels were <99th percentile of control subjects in the majority of children. However, 37 children exhibited elevated antibody levels; these were most frequently detected at the age of 2 years. The antibody prevalence at age 2 years was 2.3% for ICA, 7% for IAA, 4.2% for GADA, and 2.8% for IA-2A (8.9% positive for at least one antibody). Children of diabetic fathers were positive for at least one antibody more frequently than were children of diabetic mothers (9 months of age: 8.5 vs. 3.6%; 2 years of age: 16.7 vs. 7.9%). There was no specific sequence in the appearance of positive autoantibodies, but 13 (35%) antibody-positive cases already had more than one ICA before the age of 2 years and 7 (19%) showed reactivity to three islet cell antigens before age 5 years. The presence of multiple antibodies confers high risk for the future development of diabetes; three of six children who exhibited positive antibody responses to all four antibodies tested and another child with two positive antibodies developed clinical diabetes at the ages of 13, 21, and 27 months and 5 years. We conclude that loss of tolerance to beta-cell autoantigens and appearance of autoimmune phenomena occur very early in life in individuals with genetic susceptibility for IDDM. Screening programs to identify candidates for disease-prevention therapies can therefore be focused on this young age-group, in whom the disease process may be less advanced and who may therefore be best suited to such therapies.

Cellular immune response to diverse islet cell antigens in IDDM

In IDDM, T-cells are postulated to mediate the destruction of pancreatic beta-cells. We analyzed peripheral blood mononuclear cell (PBMC) responses to human insulin, glutamate decarboxylase GAD65, tyrosine phosphatase ICA512, glucagon, membrane preparations of RIN cells and human pancreas, and three control antigens (La = nuclear cell antigen, tetanus toxoid, and phytohemagglutinin). A total of 28 patients with newly diagnosed IDDM, 9 antibody-positive (Ab+) first-degree relatives, and 16 healthy control subjects were included. Increased proliferative responses to pancreatic islet cell antigens were observed in diabetic patients and in Ab+ relatives compared with control subjects, whereas T-cell reactivity to nonpancreatic control antigens was similar between the study groups. The highest differences in the magnitude of proliferative responses were seen for ICA512, followed by membrane preparations of RIN cells, GAD65, and human pancreas. Few subjects reacted with insulin or glucagon. Interestingly, Ab+ relatives showed higher T-cell reactivity with respect to stimulation indexes and prevalences than newly diagnosed diabetic patients, and as many as 89% of Ab+ relatives showed proliferation to more than one islet cell antigen preparation in comparison to 43% of newly diagnosed diabetic patients and none of the control subjects. Statistical analysis revealed significant positive correlation of insulin autoantibody levels with the levels of insulin-specific T-cells in Ab+ relatives, but no relation of PBMC responses to age, sex, or HLA-DR haplotypes. Our results demonstrate the simultaneous existence of various autoreactive T-cells specific for islet cell antigens in the prediabetic period. These T-cells may play a significant role in the pathogenesis of the disease.

Glutamic acid decarboxylase and other autoantigens in IDDM

Autoantigens in insulin-dependent diabetes serve as diagnostic markers and as potential therapeutic immunomodulators. Recent studies have focused particularly on two well studied molecules, glutamic acid decarboxylase and insulin, as well as several new antigens that have been recently identified, recognized by antibody and/or cell-mediated immune responses in diabetic patients. Temporal aspects of antigen exposure, antigen processing of specific peptide antigens, and the interplay between specific antigens, MHC genetics, and host T-cell responses remain to be explored.

Induction of insulin antibodies and insulin allergy under alpha-interferon treatment of renal cell carcinoma in a patient with insulin-treated diabetes mellitus--a case report

The induction of insulin antibodies and the development of an insulin allergy were observed in a male diabetic patient treated with insulin during alpha-IFN therapy of renal cell carcinoma. Diabetes and renal cell carcinoma were diagnosed at the same time. The patient was treated with biosynthetic human insulin and nephrectomy was performed. Four months later, antineoplastic chemotherapy was started (alpha-IFN, vinblastin). Six weeks after initiation of alpha-IFN injections, the patient reported signs of insulin allergy. Significant titers of insulin antibodies of both the IgG and IgE subclasses were found in the serum at that time and during follow-up, but not before the treatment with alpha-IFN. None of the other autoantibodies investigated were positive.

The potential immunogenicity of human insulin and insulin analogues evaluated in a transgenic mouse model

Transgenic mice with tissue-specific expression of the human insulin gene in the beta cells of the pancreas do not produce insulin-specific antibodies when injected with human insulin. Tolerant transgenic mice injected with human or porcine insulin reflect the clinical situation. When injected with bovine insulin the transgenic mice produce antibodies. The potential immunogenicity of 12 recombinant human insulin analogues has been tested in this transgenic model. The analogues were designed either to prevent hexamer formation or to improve chemical stability or both. The analogues have amino acid substitutions or deletions at residue 8, 10 and 21 in the A-chain and residue 3, 9, 27 and 28 in the B-chain. The results show that substitution of single amino acids in the A-chain loop of human insulin for the corresponding amino acids in bovine insulin at residues A8 or A10 is sufficient to elicit an antibody response in responder mice. Only human insulin analogues with substitutions at residues 8 or 10 in the A-chain elicit antibody formation in the transgenic mice, whereas non-transgenic control groups respond to insulin and all analogues. Antibodies developed against the human insulin analogues are cross reactive with recombinant human insulin. Antibodies developed against an immunogenic analogue could therefore neutralize both the analogue and the native insulin and thereby aggravate the patient's condition. This transgenic mouse immunogenicity model should be useful as an in vivo model to map immunogenic areas of recombinant proteins.