Time-Resolved Autoantibody Profiling Facilitates Stratification of Preclinical Type 1 Diabetes in Children

Progression to clinical type 1 diabetes varies among children who develop β-cell autoantibodies. Differences in autoantibody patterns could relate to disease progression and etiology. Here we modeled complex longitudinal autoantibody profiles by using a novel wavelet-based algorithm. We identified clusters of similar profiles associated with various types of progression among 600 children from The Environmental Determinants of Diabetes in the Young (TEDDY) birth cohort study; these children developed persistent insulin autoantibodies (IAA), GAD autoantibodies (GADA), insulinoma-associated antigen 2 autoantibodies (IA-2A), or a combination of these, and they were followed up prospectively at 3- to 6-month intervals (median follow-up 6.5 years). Children who developed multiple autoantibody types (n = 370) were clustered, and progression from seroconversion to clinical diabetes within 5 years ranged between clusters from 6% (95% CI 0, 17.4) to 84% (59.2, 93.6). Children who seroconverted early in life (median age <2 years) and developed IAA and IA-2A that were stable-positive on follow-up had the highest risk of diabetes, and this risk was unaffected by GADA status. Clusters of children who lacked stable-positive GADA responses contained more boys and lower frequencies of the HLA-DR3 allele. Our novel algorithm allows refined grouping of β-cell autoantibody-positive children who distinctly progressed to clinical type 1 diabetes, and it provides new opportunities in searching for etiological factors and elucidating complex disease mechanisms.

Early prediction of autoimmune (type 1) diabetes

Underlying type 1 diabetes is a genetic aetiology dominated by the influence of specific HLA haplotypes involving primarily the class II DR-DQ region. In genetically predisposed children with the DR4-DQ8 haplotype, exogenous factors, yet to be identified, are thought to trigger an autoimmune reaction against insulin, signalled by insulin autoantibodies as the first autoantibody to appear. In children with the DR3-DQ2 haplotype, the triggering reaction is primarily against GAD signalled by GAD autoantibodies (GADA) as the first-appearing autoantibody. The incidence rate of insulin autoantibodies as the first-appearing autoantibody peaks during the first years of life and declines thereafter. The incidence rate of GADA as the first-appearing autoantibody peaks later but does not decline. The first autoantibody may variably be followed, in an apparently non-HLA-associated pathogenesis, by a second, third or fourth autoantibody. Although not all persons with a single type of autoantibody progress to diabetes, the presence of multiple autoantibodies seems invariably to be followed by loss of functional beta cell mass and eventually by dysglycaemia and symptoms. Infiltration of mononuclear cells in and around the islets appears to be a late phenomenon appearing in the multiple-autoantibody-positive with dysglycaemia. As our understanding of the aetiology and pathogenesis of type 1 diabetes advances, the improved capability for early prediction should guide new strategies for the prevention of type 1 diabetes.

Insulin degludec does not increase antibody formation versus insulin glargine: an evaluation of phase IIIa trials

We examined insulin antibody formation in patients with type 1 (T1D) or type 2 diabetes (T2D) treated with once-daily insulin degludec (IDeg) or insulin glargine (IGlar) to evaluate the impact of antibody formation on efficacy and safety. Insulin antibodies were measured using subtraction radioimmunoassays in six phase IIIa clinical trials using IDeg (n = 2250) and IGlar (n = 1184). Spearman's correlation coefficient was used to evaluate associations between cross-reacting antibodies and change from baseline glycated haemoglobin (HbA1c) and insulin dose. IDeg- and IGlar-specific antibodies remained low [<1% bound/total radioactivity (B/T)] and with low levels of antibodies cross-reacting with human insulin in patients with T1D (<20% B/T) and T2D (<6% B/T). Spearman's correlation coefficients between insulin antibody levels and change in HbA1c or insulin dose were low in both treatment groups. No clinically meaningful differences in adverse event (AE) rates were observed in patients with >10% B/T or without an absolute increase in antibodies cross-reacting with human insulin. IDeg treatment resulted in few immunogenic responses in patients with T1D and T2D; antibody formation was not associated with change in HbA1c, insulin dose or rates of AEs.

[B cells from streptozotocin-induced mouse diabetic model inhibit insulin secretion of MIN-6 cells and promote production of insulin autoantibody]

OBJECTIVE

To explore the role of B cells in the progression of mouse diabetes induced by streptozotocin (STZ).

METHODS

The ICR mouse diabetic model was induced by low-dose STZ injection. Radioimmunoassay was performed to examine the serum levels of insulin, and ELISA was conducted to detect insulin autoantibody (IAA). B cells from STZ-treated mice and control group were sorted by CD19 magnetic activated cell sorting (MACS), and cell purity was verified by flow cytometry. The PBS-treated MIN-6 cells were used as blank control group (group A); the isolated normal mouse B cells were incubated with MIN-6 cells as group B; B cells isolated from normal mice were pre-stimulated with 20 μg/mL lipopolysaccharides (LPS), then were incubated with MIN-6 cells, as group C; and B cells isolated from STZ-treated mice were incubated with MIN-6 cells, as group D. The mRNA and protein levels of insulin were detected by quantitative real-time PCR (qRT-PCR) and radioimmunoassay, respectively. The levels of IAA and transforming growth factor β(TGF-β) were detected by ELISA.

RESULTS

Compared with group A, STZ-treated mice showed reduced body mass and serum insulin, but increased blood glucose and IAA levels. Flow cytometry indicated that the proportion of CD19(+) B cells were 98%. Compared with group A or B, group C or D presented with decreased mRNA and protein levels of insulin in MIN-6 cells, simultaneously, increased expressions of IAA and TGF-β.

CONCLUSION

B cells isolated from STZ-treated mice promotes the production of IAA and inhibits the secretion of insulin in MIN-6 cells.

Predictors of Progression From the Appearance of Islet Autoantibodies to Early Childhood Diabetes: The Environmental Determinants of Diabetes in the Young (TEDDY)

OBJECTIVE

While it is known that there is progression to diabetes in <10 years in 70% of children with two or more islet autoantibodies, predictors of the progression to diabetes are only partially defined.

RESEARCH DESIGN AND METHODS

The Environmental Determinants of Diabetes in the Young (TEDDY) study has observed 8,503 children who were at increased genetic risk for autoimmune diabetes. Insulin autoantibodies (IAAs), GAD65 autoantibodies (GADAs), and insulinoma-associated protein 2 autoantibodies (IA-2As) were measured every 3 months until 4 years of age and every 6 months thereafter; if results were positive, the autoantibodies were measured every 3 months.

RESULTS

Life table analysis revealed that the cumulative incidence of diabetes by 5 years since the appearance of the first autoantibody differed significantly by the number of positive autoantibodies (47%, 36%, and 11%, respectively, in those with three autoantibodies, two autoantibodies, and one autoantibody, P < 0.001). In time-varying survival models adjusted for first-degree relative status, number of autoantibodies, age at first persistent confirmed autoantibodies, and HLA genotypes, higher mean IAA and IA-2A levels were associated with an increased risk of type 1 diabetes in children who were persistently autoantibody positive (IAAs: hazard ratio [HR] 8.1 [95% CI 4.6-14.2]; IA-2A: HR 7.4 [95% CI 4.3-12.6]; P < 0.0001]). The mean GADA level did not significantly affect the risk of diabetes.

CONCLUSIONS

In the TEDDY study, children who have progressed to diabetes usually expressed two or more autoantibodies. Higher IAA and IA-2A levels, but not GADA levels, increased the risk of diabetes in those children who were persistently autoantibody positive.

Electrochemiluminescence assays for insulin and glutamic acid decarboxylase autoantibodies improve prediction of type 1 diabetes risk

We recently developed new electrochemiluminescence (ECL) insulin autoantibody (IAA) and glutamic acid decarboxylase 65 autoantibody (GADA) assays that discriminate high-affinity, high-risk diabetes-specific autoantibodies from low-affinity, low-risk islet autoantibodies (iAbs) detected by radioassay (RAD). Here, we report a further validation of the ECL-IAA and -GADA assays in 3,484 TrialNet study participants. The ECL assay and RAD were congruent in those with prediabetes and in subjects with multiple autoantibodies, but only 24% (P<0.0001) of single RAD-IAA-positive and 46% (P<0.0001) of single RAD-GADA-positive were confirmed by the ECL-IAA and -GADA assays, respectively. During a follow-up (mean, 2.4 years), 51% of RAD-IAA-positive and 63% of RAD-GADA-positive subjects not confirmed by ECL became iAb negative, compared with only 17% of RAD-IAA-positive (P<0.0001) and 15% of RAD-GADA-positive (P<0.0001) subjects confirmed by ECL assays. Among subjects with multiple iAbs, diabetes-free survival was significantly shorter if IAA or GADA was positive by ECL and negative by RAD than if IAA or GADA was negative by ECL and positive by RAD (P<0.019 and P<0.0001, respectively). Both positive and negative predictive values in terms of progression to type 1 diabetes mellitus were superior for ECL-IAA and ECL-GADA, compared with RADs. The prevalence of the high-risk human leukocyte antigen-DR3/4, DQB1*0302 genotype was significantly higher in subjects with RAD-IAA or RAD-GADA confirmed by ECL. In conclusion, both ECL-IAA and -GADA are more disease-specific and better able to predict the risk of progression to type 1 diabetes mellitus than the current standard RADs.

Interleukin-21 is required for the development of type 1 diabetes in NOD mice

OBJECTIVE

Interleukin (IL)-21 is a type 1 cytokine that has been implicated in the pathogenesis of type 1 diabetes via the unique biology of the nonobese diabetic (NOD) mouse strain. The aim of this study was to investigate a causal role for IL-21 in type 1 diabetes.

RESEARCH DESIGN AND METHODS

We generated IL-21R-deficient NOD mice and C57Bl/6 mice expressing IL-21 in pancreatic beta-cells, allowing the determination of the role of insufficient and excessive IL-21 signaling in type 1 diabetes.

RESULTS

Deficiency in IL-21R expression renders NOD mice resistant to insulitis, production of insulin autoantibodies, and onset of type 1 diabetes. The lymphoid compartment in IL-21R-/- NOD is normal and does not contain an increased regulatory T-cell fraction or diminished effector cytokine responses. However, we observed a clear defect in autoreactive effector T-cells in IL-21R-/- NOD by transfer experiments. Conversely, overexpression of IL-21 in pancreatic beta-cells induced inflammatory cytokine and chemokines, including IL-17A, IL17F, IFN-gamma, monocyte chemoattractant protein (MCP)-1, MCP-2, and interferon-inducible protein-10 in the pancreas. The ensuing leukocytic infiltration in the islets resulted in destruction of beta-cells and spontaneous type 1 diabetes in the normally diabetes-resistant C57Bl/6 and NOD x C57Bl/6 backgrounds.

CONCLUSIONS

This work provides demonstration of the essential prodiabetogenic activities of IL-21 on diverse genetic backgrounds (NOD and C57BL/6) and indicates that IL-21 blockade could be a promising strategy for interventions in human type 1 diabetes.

Antibody response to insulin in children and adolescents with newly diagnosed Type 1 diabetes

AIMS

To compare levels of insulin antibodies in children and adolescents after initiation of insulin therapy using either insulin aspart (IAsp) or human insulin (HI) in combination with Neutral Protamine Hagedorn (NPH) insulin, and to investigate the relationships between insulin antibodies and HbA(1c) and insulin dose.

METHODS

IAsp-specific antibodies (IAsp-Ab) and antibodies cross-reacting with HI and IAsp (HI-cross-Ab) were analysed by radioimmunoassay at diagnosis of diabetes and every 3-6 months for 30 months. Seventy-two patients (HI = 30, IAsp = 42) with Type 1 diabetes, aged 2-17 years were included. Data on HbA(1c), insulin dose and serious adverse events (SAEs) were collected retrospectively.

RESULTS

IAsp-Ab levels remained low throughout the study. After 9 months, the level of HI-cross-Ab increased [mean (SD) HI, 48.8% (21.53); IAsp, 40.2% (17.92)] and remained elevated. Repeated measurement analysis of HI-cross-Ab levels showed no significant difference between treatments (P = 0.16). HI-cross-Ab were significantly associated with total insulin dose (U/kg) (P = 0.001) and time (P < 0.0001), but not with HbA(1c) (P = 0.24). Mean (+/- SD) HbA(1c) was similar at diagnosis (HI 9.5 +/- 1.97%; IAsp 9.6 +/- 1.62%); HbA(1c) then decreased and stabilized to about 6.0% in both groups. Few SAEs were reported, the majority being hypoglycaemic episodes.

CONCLUSIONS

Treatment with IAsp and with HI was associated with an increase in HI-cross-Ab in insulin-naive children, but this did not influence treatment efficacy or safety. These results support the safe use of IAsp in children and adolescents with Type 1 diabetes.

Severe hypoglycaemia in a person with insulin autoimmune syndrome accompanied by insulin receptor anomaly type B

AIMS

A rare case of the insulin autoimmune syndrome (IAS) accompanied by insulin receptor anomaly is reported.

METHODS

Antibodies to insulin and insulin receptor were determined in the patient with severe hypoglycaemia before and after the treatment with prednisolone.

RESULTS

Titers of antibody to insulin and insulin receptors were 73.0% and 41.5%, respectively. Drug-induced lymphocyte stimulation tests were all negative for the suspicious drugs. Her HLA-DR was DRB1*0403/04051. Following steroid therapy, the formation of antibodies was suppressed and alleviated her symptoms. Scatchard analysis yielded findings specific to polyclonal antibodies.

CONCLUSIONS

The changes in autoantibodies resulted in alleviation of the hypoglycemic symptoms as a result of steroid therapy.

Identification of insulin autoantibodies of IgA isotype that preferentially target non-human insulin

Insulin autoantibodies (IAA) precede clinical type 1 diabetes in children. Immunization events leading to IAA are unknown. The aim of this study was to determine whether some IAA result from mucosal immunization. IgA-IAA and binding of IAA to non-human insulin were examined in selected high and low affinity IAA-positive samples and in first IAA-positive samples from children aged <2 years. High affinity IAA (>10(9)L/mol) bound strongly to human insulin and poorly to chicken insulin. In contrast, 12/13 lower affinity IAA were chicken insulin-reactive, binding equally to human and chicken insulin (n=4), or preferentially binding chicken insulin (n=8). IgA-IAA were found in association with chicken insulin-reactive IAA, and included cases where IgA-IAA predominated over IgG-IAA. Among 20 IAA-positive children aged <2 years, one had early IgA-chicken insulin-reactive IAA that were replaced by high affinity IgG-IAA. The findings suggest that some IAA can result from immunization against molecules other than human insulin at mucosal sites.

Mature high-affinity immune responses to (pro)insulin anticipate the autoimmune cascade that leads to type 1 diabetes

Children at risk for type 1 diabetes can develop early insulin autoantibodies (IAAs). Many, but not all, of these children subsequently develop multiple islet autoantibodies and diabetes. To determine whether disease progression is reflected by autoantibody maturity, IAA affinity was measured by competitive radiobinding assay in first and subsequent IAA-positive samples from children followed from birth in the BABYDIAB cohort. IAA affinity in first positive samples ranged from less than 10(6) l/mol to more than 10(11) l/mol. High affinity was associated with HLA DRB1*04, young age of IAA appearance, and subsequent progression to multiple islet autoantibodies or type 1 diabetes. IAA affinity in multiple antibody-positive children was on average 100-fold higher than in children who remained single IAA positive or became autoantibody negative. All high-affinity IAAs required conservation of human insulin A chain residues 8-13 and were reactive with proinsulin. In contrast, most lower-affinity IAAs were dependent on COOH-terminal B chain residues and did not bind proinsulin. These data are consistent with the concept that type 1 diabetes is associated with sustained early exposure to (pro)insulin in the context of HLA DR4 and show that high-affinity proinsulin-reactive IAAs identify children with the highest diabetes risk.

Nondepleting anti-CD4 monoclonal antibody prevents diabetes and blocks induction of insulin autoantibodies following insulin peptide B:9-23 immunization in the NOD mouse

INTRODUCTION

Insulin peptide B:9-23 is a major autoantigen in type 1 diabetes that induces insulin autoantibodies and prevents diabetes in the NOD. However, immunization with peptide without adjuvant may be insufficient to reverse disease or induce long-term tolerance. Furthermore, recent experience has demonstrated the potential dangers of disease exacerbation or anaphylaxis with peptide immunotherapy.

METHODS

Combination therapy of B:9-23 with a nondepleting anti-CD4 monoclonal antibody (YTS 177.9) was studied in female NOD mice from 4 through 6 weeks of age. Injections of either B:9-23 in saline, YTS 177.9 antibody, or both peptide and antibody were given to mice.

RESULTS

By 52 weeks follow-up, 40% of B:9-23-treated, 100% of YTS177.9-treated, and 70% of B:9-23 and YTS177.9 combination-treated mice remained diabetes-free. IAA, both spontaneous and induced by B:9-23, was almost completely suppressed in mice receiving YTS 177.9. In addition to suppression of IAA expression, anti-B:9-23 peptide antibodies are also suppressed in mice receiving B:9-23 with YTS 177.9, compared to B:9-23 alone.

CONCLUSION

A brief course of the nondepleting anti-CD4 monoclonal antibody (YTS 177.9) in NOD mice confers long-term protection from diabetes and insulitis and profoundly blocks spontaneous and B:9-23 peptide-induced insulin autoantibodies.

Type-1 diabetes mellitus with insufficient serum immunoreactive insulin elevation after subcutaneous NPH-insulin injection

We report a case of Type-1 diabetes with insufficient serum immunoreactive insulin (IRI) elevation after subcutaneous NPH-insulin injection. Favorable glycemic control was achieved by a continuous subcutaneous insulin infusion (CSII) using regular insulin. A 34-year-old woman with Type-1 diabetes (height 158 cm, weight 43.4 kg) was admitted to our hospital to improve glycemic control. On admission, her glycosylated hemoglobin (HbA(1c)) level was 10.9% and her fasting plasma glucose (FPG) level was 332 mg/dl. After admission, her insulin regimen was altered from two injections a day using premixed insulin to four injections a day using regular insulin before each meal and NPH insulin at bedtime. Although the dosage of NPH insulin at bedtime was increased to 32 U/day, there was no improvement in the FPG level. The peak IRI value after NPH insulin injection was not observed but that after the regular insulin injection was observed. Therefore, her insulin administration regimen was changed to CSII, using regular insulin alone. Her fasting plasma glucose level decreased, glycosylated hemoglobin (HbA(1c)) level improved to 7.0%, her body weight increased to 46.6 kg 4 months after starting CSII.

Insulin autoantibodies: more specific than proinsulin autoantibodies for prediction of type 1 diabetes

Proinsulin autoantibodies (PAA) are a potential alternative to insulin autoantibodies (IAA) for the prediction of type 1 diabetes. We measured the prevalence of PAA and IAA in 179 patients with newly diagnosed type 1 diabetes and 1028 schoolchildren, and compared the potential of these antibodies for disease prediction. Antibodies were measured using a novel microassay in which screening for binding of radio-labelled antigen was followed by competitive displacement. Thresholds for both antigen binding and competitive displacement were selected so that equivalent numbers of patients with type 1 diabetes were identified by the proinsulin and insulin antibody assays. Similar numbers of schoolchildren were found to have insulin and proinsulin binding above the screening threshold but, after competitive displacement, the prevalence of PAA (3.7%) was more than twice that of IAA (1.4%) with 66% sensitivity. Both PAA and IAA were present in 113 (63%) of patients, as against 0.8% of schoolchildren, implying that individuals with both antibodies are at particularly high risk of disease. The majority of samples with IAA or PAA were displaced with both insulin and proinsulin, suggesting that the main epitopes recognized by these antibodies are on the insulin molecule. We conclude that IAA are more specific than PAA for the prediction of type 1 diabetes.

Insulin antibodies and hypoglycemia in diabetic patients. Can a quantitative analysis of antibody binding predict the risk of hypoglycemia?

We report a noninsulin-dependent diabetes mellitus (NIDDM) patient with spontaneous, severe hypoglycemic reactions and the presence of insulin antibodies. He had a remote antecedent history of beef-pork insulin therapy as well as exposure to hydralazine. Detailed insulin binding kinetic studies were performed in this patient as well as in six other insulin-treated diabetic patients with anti-insulin antibodies (three with and three without an obvious cause of hypoglycemia). Sera from the current patient and five of the six other diabetic patients (one NIDDM, four IDDM) revealed two types of binding sites: high-affinity with low capacity (Kd, 0.4-12.4 x 10(-9) mol/L; binding capacity, 0.6-659 mU/L) and low-affinity with high capacity (Kd, 0.3 to 35.7 x 10(-7) mol/L; binding capacity; 202-113,680 mU/L). One NIDDM patient had only high-affinity antibodies (Kd, 22.9 x 10(-9) mol/L; binding capacity of 78 mU/L). Type of diabetes mellitus, insulin antibody titers or their binding capacities, insulin levels (total, bound, or free), and bioavailable insulin were not related to hypoglycemic reactions. Two calculated values by the method described tended to discriminate patients with and without hypoglycemia. The calculated amount of low-affinity antibody bound insulin ranged from 69.4-2090 mU/L vs < 4-70.6 mU/L in patients with and without hypoglycemia, respectively. The best discrimination was afford by the percent saturation of low-affinity binding sites; values were clearly higher in the patients with hypoglycemia (2.5-34.4%) than in those without hypoglycemia (not detectable, 0.06, 0.15%). Consideration of the possible drug-associated insulin antibody formation in insulin-treated diabetics and the novel quantitative analysis of the antibody binding kinetics should prove helpful in evaluating patients with high insulin antibody titers and assessing the risk of hypoglycemia.

Anti-insulin activity in normal newborn cord-blood serum: absence of IgG-mediated insulin binding

Insulin autoantibodies (IAAs) are present in approximately 60% of type I diabetes patients at onset and are used as predictors for the disease. Although the prevalence of IAAs in the general population has been reported to be <1%, preliminary data have pointed out a higher proportion of IAA positivity in newborn cord-blood serum, and some authors have suggested that they are immunoglobulin G antibodies, resulting from a hypothetical gestational insulitis. To characterize this insulin-binding activity, we analyzed cord-blood sera from 100 healthy newborns, as well as serum from 21 of their mothers at delivery, 179 new-onset type I diabetic patients, and 200 healthy control subjects. IAAs were present in 0.5% of the control subjects and 54% of new-onset type I diabetic patients. On the other hand, 96% of the newborn cord-blood sera showed anti-insulin activity, while it was detected in only 14% of their mothers. No significant differences were observed between cord sera and the general population for islet-cell or anti-GAD autoantibodies. Anti-insulin activity in cord serum was not bound by protein A or protein G, in contrast with type I diabetes-related IAA activity. We conclude that this insulin-binding activity, present in most newborn cord sera and specific to the child, is not IgG mediated. These data, together with the absence of other pancreatic autoimmunity markers in this population, suggest that it is an isolated phenomenon not related to type I diabetes or other pancreatic autoimmune processes and is due to the presence of a cross-reacting molecule in cord blood that has yet to be identified.

[Therapeutic complications from insulin antibodies--two case reports]

Immunological complications of insulin therapy are extremely rare, since highly purified insulins, especially human semi- or biosynthetic insulin preparations became available for treatment of diabetes mellitus. Insulin antibodies of the immunoglobulin G or immunoglobulin E class can develop in 10-60%, however, in low titers in patients treated exclusively with human insulin. In rare cases these antibodies assume clinical significance, if the antigenic potential of the insulin used is high enough and if genetic predisposition exists. Two case reports presented here confirm this concept.

Characterization of insulin autoantibodies in a patient with autoimmune hypoglycemia

A 60-year-old man referred because of hypoglycemic bouts was found to have insulin autoantibodies. Total plasma insulin was as high as 1.44 nmol/l. Both plasma free insulin and C-peptide were in the normal range. The indirect immunofluorescence technique showed positivity for antinuclear antibodies. The T-lymphocyte populations in the peripheral blood were normal. When serum binding capacity for pork insulin was measured, antibodies binding pork insulin were not detected. The patient's serum bound 125I-insulin. The binding protein was identified to be an immunoglobulin G. The kinetics of dissociation, studied by the Scatchard analysis of the autoantibody, showed a curvilinear plot, which was analyzed in two components. Cold human insulin was able to compete with 125I-insulin for the antibody binding site (I.C.50 = 1.35 nmol/ml). These antibodies were apparently not associated with antibodies directed against the insulin receptor.

A direct two-site peroxidase-based enzyme-linked immunosorbent assay for proinsulin

A non-competitive sandwich assay using an anti-C-peptide IgG and an anti-insulin IgG was developed to measure fasting levels of proinsulin in human serum. The former antibody provided the lower layer in a sandwich immunoassay, the upper layer being composed of an anti-insulin IgG-horse radish peroxidase conjugate. The assay showed negligible cross reactivity at supraphysiological levels of insulin and C-peptide. The method enabled the estimation of proinsulin in fasting non-diabetic control subjects [13.7 +/- 1.6(4) pM] and in type 2 non-insulin-dependent diabetic patients [23.2 +/- 1.1(8) pM].

Immunocytochemical verification of the insulin receptor's specificity in the nuclear envelope of Tetrahymena. Comparison with receptors of the plasma membrane

The unicellular Tetrahymena possess hormone receptors in the nuclear envelope similarly to higher rank animals. These receptors bind insulin and their specificity is detectable by monoclonal antibodies developed to insulin. The hormonal (insulin) pretreatment (imprinting) of the cell did not alter the binding capacity of the nuclear membrane, demonstrated by antibody-technique. The specific binding characteristics of the plasma membrane was demonstrated and this was significantly increased following imprinting. In the nucleus of Tetrahymena presence of insulin was not detected by immunocytochemical method.

Jet-injected insulin is associated with decreased antibody production and postprandial glucose variability when compared with needle-injected insulin in gestational diabetic women

OBJECTIVE

To elucidate the glycemic response and antibody formation in gestational diabetic women treated with insulin injected by a needle or a jet. The American Diabetes Association's position statement on jet injectors raised the concern that "insulin could be denatured as a result of forceful injection through a tiny port, which could lead to an increase in antibody formation" (Diabetes Care 11:600, 1988). However, the pharmacokinetics of jet-injected insulin suggest that it might be useful in controlling postprandial glucose levels.

METHODS

We randomized 20 women with gestational diabetes mellitus (< 34 wk gestation) who required insulin to receive either jet-injected or needle-injected human NPH and regular insulin. Variables of interest were evaluated at the start of therapy, weekly until delivery, and 6-wk postpartum that included: 1) insulin antibodies in the mother and her infant, 2) HbA1c, 3) insulin dose, 4) fasting and postprandial glucose levels, and 5) subject acceptance and preference.

RESULTS

Of the 10 women in the needle group, 6 developed significant insulin antibodies compared with 1 of 10 in the jet group (P < 0.001). HbA1c and insulin doses were the same in both groups. During the test meal, glucose levels in the jet group were significantly lower (P < 0.01), yet none of the women in the jet group experienced blood glucose < 70 mg/dl (3.89 mM) at 3-4 h after the meal, compared with 5 in the needle group (P < 0.001). Jet injection was associated with less variability (P < 0.001) in postprandial glucose values but slightly greater variability (P < 0.05) in fasting glucose. Jet-injected insulin was more readily accepted by subjects than needle injections.

CONCLUSIONS

Jet injection is associated with a diminished antibody response and postprandial variability compared with needle-injected insulin. Thus, this warrants consideration as a therapeutic option for women with gestational diabetes mellitus and may also be applicable to nonpregnant, insulin-requiring diabetic patients.

Autoantibodies to insulin have similar affinity to that of antibodies to exogenous insulin but lower binding capacity

The binding characteristics of insulin autoantibodies (IAA) were compared with those of antibodies to exogenous insulin (IBA) by analyzing the specific binding, binding capacity and affinity for insulin in 11 children (age range 1.5-13.0 years) with insulin-dependent diabetes (IDDM) both at diagnosis and after 1 year of insulin treatment. Maximal specific insulin binding was 7.8 (1.5; SE) pmol l-1 for IAA and 28.1 (6.7) pmol l-1 for IBA (P < 0.01), and the binding capacity of the high affinity class of IAA 0.01 (0.003) nmol l-1, as compared with 0.19 (0.08) nmol l-1 for the corresponding IBA class (P < 0.01). With regard to the low-affinity components the binding capacity was 0.11 (0.05) nmol l-1 for IAA and 1.50 (0.95) nmol l-1 for IBA (P < 0.01). No differences in the affinity constants could be observed between IAA and IBA. There was no correlation between the insulin binding of IAA and quantitative levels of islet cell antibodies (ICA) at the clinical presentation or subsequent IBA values. The specific insulin binding of IBA correlated negatively with serum C-peptide concentrations and positively with HbA1 levels at 1 year. The present observations suggest that IAA developing before the diagnosis of IDDM are characterized by a reduced binding capacity as compared with antibodies to exogenous insulin, whereas they have a similar affinity for insulin. IAA seem to be quantitatively unrelated to ICA and postdiagnostic IBA levels. High IBA levels appear to be associated with reduced endogenous insulin secretion and poor metabolic control during the early clinical course of the disease.

Randomized trial of human versus animal species insulin in diabetic pregnant women: improved glycemic control, not fewer antibodies to insulin, influences birth weight

OBJECTIVE

Macrosomia occurs in infants of diabetic mothers in spite of "nearly normal maternal blood glucose levels" with insulin treatment. Insulin antibodies may carry bound insulin into the fetal blood and thus may be associated with fetal hyperinsulinemia and macrosomia in these infants. Our objective was to test the hypothesis that human insulin is associated with lower insulin antibody levels and less macrosomia than is animal species insulin.

STUDY DESIGN

Forty-three insulin-requiring pregnant (< 20 weeks' gestation) women, previously treated with animal insulin, were randomized to human and animal insulins and studied at weeks 10 through 20, 24, 28, 32, 36, and 38, at delivery, and at 3 months post partum. Infant blood was drawn at delivery (cord) and at 1 day and 3 months post partum 1 hour after a glucose-amino acid challenge.

RESULTS

Women receiving human insulin required significantly less insulin per kilogram of body weight and showed significant dampening of glucose excursions (p < 0.05 for each comparison). Infants born to mothers receiving human insulin weighed 2880 +/- 877 gm compared with 3340 +/- 598 gm for infants of women treated with animal insulin (p < 0.05). There was no difference in insulin antibody levels between groups for either mothers or infants. Infants born to mothers receiving human insulin had a 1 hour C-peptide level after the glucose-amino acid challenge at 3 months of age of 0.21 +/- 0.13 pmol/ml compared with 0.32 +/- 0.13 pmol/ml (p = 0.01).

CONCLUSION

Administration of human insulin to pregnant diabetic women has a therapeutic advantage over animal insulin, with less maternal hyperglycemia or hypoglycemia, fewer larger-for-gestational-age infants, and less neonatal hyperinsulinemia. Our data do not support the hypothesis that maternal antibodies to insulin influence infant birth weight.

Longitudinal study of islet cell antibodies and insulin autoantibodies and development of diabetes in non-obese diabetic (NOD) mice

We have previously shown the presence of circulating islet cell cytoplasmic antibodies (ICA) and insulin autoantibodies (IAA) in the NOD mouse before onset of insulin-dependent diabetes mellitus (IDDM). Here we have determined the levels of the two autoantibodies in 28 female NOD mice longitudinally from approximately day 40 to day 250, to examine their ontogeny, association and predictive value for diabetes. All animals (11 diabetic, 17 non-diabetic) showed varying levels of ICA at some stage, while IAA activity was found in 21 out of 28 mice. Expression of both the markers was seen in more than half of the animals by day 60, with higher levels and rates occurring subsequently in both diabetic and non-diabetic groups. The expression of ICA did not always correlate with that of IAA. There was no apparent difference in the ontogeny of ICA and IAA between the two groups. During the study period the number of animals with ICA was similar in the two groups, while the number of those with IAA was higher in the diabetic animals. In this group declining and rising levels of ICA were seen just before clinical diabetes with frequent peaks of IAA. In the same animals, eight out of 11 mice showed co-expression of high levels of both markers either intermittently or persistently prior to onset, whereas only one non-diabetic animal showed this. We conclude that the ontogeny and serum level of ICA or IAA alone could not be used to predict the clinical onset of diabetes in these animals. However, co-expression of high levels of both markers prior to onset may suggest a strong predisposition to clinical diabetes. This may have relevance to attempts to predict the onset of IDDM in humans who have one or both of these immunological markers.

Deleterious effect of anti-insulin antibodies on diabetes control

We studied the effect of anti-insulin antibodies (AIA) on glycemia control in patients with insulin-dependent diabetes (IDD) by following the AIA titer changes with time. Although expected to remain constant, AIA levels were found to either increase or decrease in most patients. These AIA titer changes correlated significantly with changes in glycohemoglobin but not with changes in insulin dose. The results suggest that AIA may have a deleterious effect on glycemia control in IDD.

Prolonged fasting hypoglycemia due to insulin antibodies in patient with non-insulin-dependent diabetes mellitus: effect of insulin withdrawal on insulin-antibody-binding kinetics

Fasting hypoglycemia, which persisted for 3 days after insulin treatment was stopped, occurred in a patient with non-insulin-dependent diabetes mellitus who had inappropriate plasma free-insulin levels (18-25 microU/ml) and extremely high antibody-bound insulin (greater than 20,000 microU/ml) but normal counter-regulatory hormone secretion and plasma C-peptide levels. The amount of antibody-bound insulin decreased in a biphasic pattern over 13 mo of observation with an initial half-life of 35 days and a more gradual decrease with a half-life of 160 days. The number of high-affinity antibody binding sites was virtually identical to the amount of antibody-bound insulin in the patient's plasma. We conclude that the patient's fasting hyperinsulinemia and hypoglycemia were due to release of antibody-bound insulin.

The intravenous insulin tolerance test in type I diabetes

The intravenous insulin tolerance test (ITT) allows general assessment of insulin sensitivity by determining the fall in plasma glucose after injection of 0.1 unit/kg regular insulin. To evaluate the usefulness of this test diagnostically in distinguishing Type I from Type II diabetes, 24 patients with Type I diabetes (defined as early age of onset, ideal body weight or less at onset, and insulin dependence) underwent ITTs. Seven patients had normal glucose disposal rates (Ki greater than or equal to 2.5. Nine patients had Ki less than 2.5 but greater than 1.0. Eight patients had Ki less than 1.0. The slopes did not correlate with the control of the diabetes (as assessed by measurement of glycosylated hemoglobin), the presence or titer of anti-insulin antibodies, the duration of the diabetes, the age of onset, the presence of complications, or the current insulin dose. These results indicate that varying amounts of insulin resistance may be present in Type I diabetes and cannot necessarily be explained by poor control or the presence of insulin antibodies.

Sample preparation and radioimmunoassay for circulating free and antibody-bound insulin concentrations in insulin-treated diabetics: a re-evaluation of methods

Methods for blood sample preparation and radioimmunoassay of free and antibody-bound serum or plasma insulin concentrations, using polyethylene glycol (PEG) solution to precipitate bound insulin, have been evaluated and compared. Method A was rapid mixing of whole blood with PEG, followed by separation of bound insulin by centrifugation into Ficoll; method B was rapid PEG addition to whole blood, followed by centrifugation alone; method C was conventional PEG addition to thawed plasma or serum, followed by centrifugation to remove bound insulin. Method A was found to have acceptable performance and reproducibility; serum free insulin levels were not significantly different from those measured by the simpler method B. In samples from insulin-dependent diabetics, serum free insulin was significantly higher and bound insulin significantly lower in method A compared to the conventional method C. However, in samples from non-diabetics there was no significant difference between methods A and C. Spurious results were obtained by addition of PEG and assay of plasma and serum samples after either freezing and thawing or incubation at 37 degrees C for 2h, compared to PEG addition and assay of fresh plasma or serum samples. We conclude that conventional, delayed addition of PEG to plasma or serum may result in redistribution of free and bound insulin and that values more representative of in vivo blood insulin levels are obtained by rapid PEG addition methods.

Meal-stimulated C-peptide and insulin antibodies in type I diabetic subjects and their nondiabetic siblings characterized by HLA-DR antigens

We studied serum C-peptide (CP) response 90 min after a breakfast meal and insulin antibody titers in 171 type I diabetic (IDDM) patients and 272 of their nondiabetic siblings from 169 unrelated families. HLA typing was performed in all participants. In IDDM patients, there was a decline in CP response with increased duration of disease. CP responses of greater than or equal to 1.8 ng/ml were seen significantly less often in patients who were less than 10 yr old at the time of diagnosis of IDDM than in patients who were greater than 10 yr old at the time of diagnosis (8% versus 21%, P less than 0.05). More patients with HLA-DR4 had a CP response greater than or equal to 1.8 ng/ml than did patients who lacked this antigen whether duration of IDDM was less than 10 yr (30% versus 18%, P greater than 0.05) or greater than or equal to 10 yr (15% versus 0%, P less than 0.05). Mean C-peptide was also higher in HLA-DR4-positive patients compared with HLA-DR4-negative patients both when duration of disease was less than 10 yr (1.7 +/- 1.9 versus 1.4 +/- 1.0, P less than 0.01) and greater than or equal to 10 yr (1.2 +/- 1.5 versus 1.0 +/- 0.4, P less than 0.0001). Insulin antibody binding was slightly higher in patients with HLA-DR4 compared with patients lacking this antigen (5.96 +/- 7.20 versus 4.89 +/- 4.74, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Binding of insulin to its receptor impairs recognition by monoclonal anti-insulin antibodies

The interaction between insulin and its receptor was investigated using both monoclonal and polyclonal anti-insulin antibodies. After covalent cross-linking of 125I-insulin to the insulin receptor on cultured human lymphocytes (IM-9 cells) using disuccinimidyl suberate, we inquired whether the insulin-receptor complex could be immunoprecipitated with anti-insulin antibodies. While a polyclonal guinea pig anti-insulin antiserum succeeded in immunoprecipitating receptor-bound 125I-insulin, binding to the receptor decreased the avidity of the antiserum for the insulin moiety by a factor of approximately 1000-fold. Sixteen distinct monoclonal murine anti-insulin antibodies were employed to immunoprecipitate receptor-bound 125I-insulin. Of these 16 monoclonal antibodies, only one (antibody 5.9F4) could be shown to recognize receptor-bound 125I-insulin. Moreover, even with antibody 5.9F4, binding of 125I-insulin to its receptor reduced the affinity of the antibody by a factor of 10- to 100-fold. These data strongly suggest that, when insulin binds to its receptor, the majority of the insulin molecule is unavailable for binding by anti-insulin antibodies. It seems likely that the hormone binding site on the receptor may be very large, thereby allowing for sequestration of the majority of the insulin molecule with relatively little of the hormone remaining exposed.

Insulin resistance in patients with myotonic dystrophy

Evaluation of insulin sensitivity in 12 patients with myotonic dystrophy gave results different from those found in other insulin-resistant conditions. Nine of our subjects were insensitive to exogenous insulin, but only three had elevated fasting insulin concentrations. Eight had an excessive insulin response to a glucose challenge. Monocyte insulin receptor affinity was decreased (myotonics, 1.21 +/- 0.74 X 10(9) liters per mole; controls, 2.62 +/- 1.28 X 10(9)), and this parameter correlated best with the insulin resistance. No circulating receptor antibody or insulin binding inhibitor was found. Our studies suggest that the insulin resistance seen in patients with myotonic dystrophy is related to decreased insulin receptor affinity.

Participation of adrenal medulla in 6-amino-nicotinamide-induced hyperglycaemia in the rat

In fasted rats 6-aminonicotinamide (6-AN) produced delayed hyperglycaemia, the peak effect being seen by 7 h. Fasting plasma insulin concentrations were not significantly altered but liver glycogen concentrations were decreased following treatment with 6-AN. Adrenalectomy, demedullation and pretreatment with reserpine, phentolamine, nicotinamide and nicotinic acid completely blocked the hyperglycaemic response whereas guanethidine and propranolol or oxprenolol were ineffective. Catecholamine concentrations in the adrenal venous plasma were markedly increased by treatment with 6-AN, the peak effect being seen by 5 h. It is concluded that adrenal medullary release, which is slow in onset, is mainly responsible for the development of sustained hyperglycaemia in the rat.

Clinical significance of circulating C-peptide in diabetes mellitus and hypoglycemic disorders

Proinsulin is converted to insulin and C-peptide in the pancreatic in the pancreatic beta cells: the latter two peptides are secreted in equimolar concentrations. Thus, measurements of serum C-peptide provide a means of assessing pancreatic beta cell function in addition to that of insulin. This technique has proved particularly useful in insulin treated diabetic patients in whom the development of circulating insulin antibodies interferes with the radioimmunoassay of the hormone. The C-peptide assay has also been used to facilitate the diagnosis of various hypoglycemic conditions, including islet cell tumors and factitious injection of insulin. The extraction of C-peptide in the urine reflects average serum values over a period of time and urine C-peptide measurements are especially useful in children or individuals in whom repeated blood sampling is difficult.

Studies on experimental insulin immunity. I. Dynamics of insulin immunity in the guinea pig

Insulin half life and the formation and characterization of the insulin-binding antibodies have been studied in the guinea pig both in vivo and in vitro. The antigen-antibody complexes have also been studied utilizing cellulose column electrophoresis and Sephadex G-200 column filtration. In addition, a quantitative assay procedure for insulin-binding antibodies has been employed.

In normal guinea pigs the injected insulin-I-125 is carried by at least two serum proteins, presumably albumin and an α. globulin, or more specifically 4.5S and 19S proteins. In immune animals the insulin-antibody complexes are represented by a single peak in the (β-γ globulin region on column electrophoresis; they are distinguishable from the uncomplexed antibodies which are 7S γ1 and 7S γ1 globulins. The precipitating insulin antibody also appears to be a 7S globulin. Moreover, the insulin-antibody complexes occur as a single component in the 19S fraction on Sephadex G-200 filtration, and if the complex were a single molecule it would have a molecular weight equivalent of about 630,000.

During the immunization process the insulin binding antibody titer increases progressively in association with an elevation of 7S globulin. In most animals during the early stages of immunization the molecular weight of the antibodies appears to be exclusively of the 7S globulin type; however, in two of seven animals there was, in addition, a small amount of insulin antibody of 19S globulin type early during the immunization period.

The purpose in estimating a molecular weight equivalent of the insulin-antibody complex relates to the possibility that the distinctive features of the angiopathies of diabetes may depend upon certain physicochemical characteristics of this complex.