Insulin-binding antibody

The concept of immunoassay was first described in 1945 when Landsteiner suggested that antibodies could bind selectively to small molecules (haptens) when they were conjugated to a larger carrier molecule. This hapten-specific concept was explored by Yalow and Berson in the late 1950s, and resulted in an immunoassay that was applied to insulin monitoring in humans. This pioneering work set the stage for the rapid advancement of immunochemical methods for clinical use. 

Petruzzelli L, Herrera R, Arenas-Garcia R, Fernandez R, Bimbaum MJ, Rosen OM 1986 Isolation of a Drosophila genomic sequence homologous to the kinase domain of the human insulin receptor and detection of the phosphorylated Drosophila receptor with an anti-peptide antibody. Proc Natl Acad Sci USA 83 4710-4714 Podskalny J, McElduff A, Gorden P 1984 Insulin receptors on Chinese hamster ovary (CHO) cells altered insulin binding to glycosylation mutants. Biochem Biophys Res Commun 125 70-75... 

Insulin-binding IgG antibodies are found in about 75% of patients with type 2 diabetes using inhaled insulin (270). This is more than one would expect from the use of subcutaneous insulin. The antibodies appear to plateau after 1 year. There are no obvious clinical effects. 

Kurtz AB, Nabarro JD. Circulating insulin-binding antibodies. Diabetologia 1980 19(4) 329-34. 

Yalow RS, Berson SA (1959) Quantitative aspects of the reaction between insulin and insulin-binding antibody. J Clin Invest 38 1996-2016... 

Protein Binding. In plasma, about 5% in normal subjects, but in diabetics the binding capacity may be extremely high due to formation of insulin-binding antibodies. 

Insulin. Twelve glass test tubes are labeled, and 0.2 ml of phosphate buffer 1 is added to each tube. The two blank tubes receive 0.1 ml of phosphate buffer 2, and the remaining 10 tubes receive in duplicate 0.1 ml of five increasing dilutions of anti-insulin serum in phosphate buffer 2. A constant amount (0.1 ml) of [ I]insulin in phosphate buffer 1 is added to each tube, and the tubes are incubated at 37° for 45 min. The reaction is stopped by the addition to each tube of 5 ml of the Z-gel slurry followed by 10 ml of 0.1 Af NH Ac (pH 6.25). The contents of the tubes are mixed by inversion, and the Z-gel is collected by centrifugation (1000 g for 5 min) at room temperature. The supernatant is decanted, and the pellet is washed by resuspension in 10 ml of 0.1 M NH4AC followed by recentrifugation. The supernatant is decanted, and the amount of associated with the pellet of Z-gel is measured. Approximately 80% of the I in the preparation of [ I]insulin binds to Z-gel in the presence of excess antibody, but only 10% binds in the absence of antibody. A dilution of the... 

With the rapid increase in the incidence of diabetes among the population, it is no longer possible to satisfy the pharmaceutical requirement (estimated to be 15-20 tonnes per year in 2005) from animal sources. Furthermore, the animal-extracted insulins are slightly different from human insulin, which might cause formation of insulin-binding antibodies and allergic reactions. Porcine insulin, which differs from human insulin only by a single amino acid in position B30, can be converted to human insulin in a transpeptidation reaction, in which an alanine is replaced with a threonine [1]. 

M5. Miller, H., and Owen, G., Immuno-electrophoresis of insulin-binding antibodies. Nature 188, 67 (1960). 

Resistance to insulin is encountered in some patients, with needed doses being very high (up to 1,000 units daily). Acute resistance can accompany infections or inflammatory conditions. Resistance has been attributed to high levels of circulating insulin-binding antibodies (e.g., IgG), and a tissue insensitivity that frequently accompanies obesity known to synchronize with increasing serum levels of insulin. It should be understood that the affinity and/or number of insulin receptors can be affected by many regulators besides insulin levels. These include sulfonylureas (see later) pH, c-AMP, exercise, meals, diet, antibodies, and even other hormones. 

In a 6-month study type 2 diabetic patients were randomised to treatment with premeal inhaled insulin plus bedtime ultralente or at least two injections of subcutaneous insulin (premix human/NPH insulin) [60], HbAlc decreased similarly in both groups (0.7% vs. 0.6%), and no difference was found in the number of hypoglycaemic events. Insulin-binding antibodies increased more in the inhaled insulin group [60]. 

Despite the marked conformity in the insulin binding curves of the insulins derived from different species and exposed to one anti-pig-insulin-antiserum, a marked discrepancy between immunological inhibition of biological activity and radio-immunologi-cally measurable insulin was noted. In contrast to the well known incomplete inhibition of the biological activity of serum insulin effected by antibodies, insulin activity in the incubation medium... 

Unwanted effects. Hypoglycemia results from absolute or relative overdosage (see p. 260). Allergic reactions are rare—locally redness at injection site, atrophy of adipose tissue (lipodystrophy) systemically urticaria, skin rash, anaphylaxis. Insulin resistance can result from binding to inactivating antibodies. A possible local lipohypertrophy can be avoided by alternating injection sites. 

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