Altered processing of human insulin by B lymphocytes from an immunologically insulin-resistant type I diabetic patient

Effect of long-term exposure to insulin lispro on the induction of antibody response in patients with type 1 or type 2 diabetes

OBJECTIVE

To determine the long-term effects of insulin lispro on inducing lispro-specific, insulin-specific, and cross-reactive (reactive with both insulin lispro and human insulin) antibodies.

RESEARCH DESIGN AND METHODS

A multinational, multicenter combination of controlled and noncontrolled, open-label studies of 4.5 years' duration was designed to evaluate the long-term immunologic profile of subcutaneously administered insulin lispro. A total of 1,221 patients (men and women; 12-81 years of age) with type 1 or type 2 diabetes were enrolled. Circulating anti-insulin antibodies were measured using radioimmunoassays.

RESULTS

Insulin-specific and lispro-specific antibody responses were within the background noise levels of the assays. Significant elevations of antibody were confined to a cross-reactive antibody response. Antibody levels resulting from prior exposure to long- and short-acting insulins changed little after transfer to insulin lispro and remained within or near the baseline levels. De novo exposure to insulin lispro resulted in increases in cross-reactive but not insulin- or lispro-specific antibody levels. Cross-reactive insulin antibodies developed more readily in patients with type 1 diabetes than in those with type 2 diabetes. Long-term antibody responses tended to decrease over time and returned to baseline or near-baseline levels by the end of the long-term studies. No evidence of an anamnestic antibody response could be found in individuals treated intermittently with insulin lispro.

CONCLUSIONS

The immunogenic profile of patients treated with insulin lispro was comparable to that of patients treated with recombinant human insulin. Inductions of significant levels of specific or cross-reactive antibodies were not observed in patients who had received insulin previously. No significant antibody-dependent increases in insulin dosage requirements were noted in these patients. The incidence of insulin allergy was not different from that in patients treated with recombinant regular human insulin.

Evidence that a peptide spanning the B-C junction of proinsulin is an early Autoantigen epitope in the pathogenesis of type 1 diabetes

The expression of pro(insulin) in the thymus may lead to the negative selection of pro(insulin) autoreactive T cells and peripheral tolerance to this autoantigen in type 1 diabetes (T1D). We investigated whether proinsulin is expressed in the thymus of young nonobese diabetic (NOD) mice, whether T cells from naive NOD female mice at weaning are reactive to mouse proinsulin, and the role of proinsulin as a pathogenic autoantigen in T1D. Proinsulin II mRNA transcripts were detected in the thymus of 2-wk-old NOD mice at similar levels to other control strains. Despite this expression, proinsulin autoreactive T cells were detected in the periphery of 2- to 3-wk-old naive NOD mice. Peripheral T cells reactive to the insulin, glutamic acid decarboxylase 65 (GAD65), GAD67, and islet cell Ag p69 autoantigens were also detected in these mice, indicating that NOD mice are not tolerant to any of these islet autoantigens at this young age. T cell reactivities to proinsulin and islet cell Ag p69 exceeded those to GAD67, and T cell reactivity to proinsulin in the spleen and pancreatic lymph nodes was directed mainly against a p24-33 epitope that spans the B chain/C peptide junction. Intraperitoneal immunization with proinsulin perinatally beginning at 18 days of age delayed the onset and reduced the incidence of T1D. However, s.c. immunization with proinsulin initiated at 5 wk of age accelerated diabetes in female NOD mice. Our findings support the notion that proinsulin p24-33 may be a primary autoantigen epitope in the pathogenesis of T1D in NOD mice.

Immunological resistance to human biosynthetic insulin--effects of immunosuppression and plasmapheresis

A 55-year-old gentleman, after being treated for a short time with a diet and with Chlorpropamide, was switched to purified porcine insulin due to ketonuria and ketoacidosis. After a year the patient developed immunological insulin resistance (mean daily insulin dose: 3.72 U/kg body weight; anti-insulin antibodies 78%). In order to lower anti-insulin antibodies human recombinant DNA insulin was introduced into further therapy. Contrary to expectations, the patient did not reduce whatsoever his anti-insulin antibodies and his daily insulin dose increased up to 5.63 U/kg body weight. Introduction of combined immunosuppressive therapy (prednisone plus azathioprine) together with plasmapheresis resulted in rapid lowering of daily insulin requirement and reduction in anti-insulin antibodies. Immunosuppressive therapy was continued with 10 mg of prednisone and a year later the patients insulin daily requirement was 0.66 U/kg BW while his antibodies were 18%. The possible causes of insulin resistance to human recombinant DNA insulin are discussed as well as the advantage of combined immunosuppressive therapy together with plasmapheresis that was used for rapid lowering of insulin daily requirement and anti-insulin antibodies titer.