Insulin Binding and Free Insulin in Serum of Insulin-Treated Diabetics

Abstract

Insulin_I l25 (0.1 ml, 0.1 microCi) was added to the equal volume of serum and fraetionated on 9 x 300 mm column of Sephadex G-I00 into protein-bound (B) and free (F) insulin immediately or after 24-hour incubation. When the fractionation was performed immediately, the B/F ratio was in 10 healthy persons 0.045 ± 0.006 (just like that of label-Ied insulin preparation itself), and in twenty-six insulintreated diabetics 0,605 ± 0,073, After incubation B/F ratio were correspondingly 0.056 ± 0.011 and 2.021 ± 0.103. There was no overlapping between normals and diabetics (P < .00l), and no protein binding of insulin by normal serum was evident. At pH 3 the bound insulin dissociated, and virtually all the radioactivity appeared with free insulin fraction. Free insulin level in the serum of diabetics as determined after serum fractionation on Sephadex G-IOO was 35.8 ± 4.0 micro V/mi only and did not conelate with B/F ratios; ,insulin dose or blood glucose. No (free)-hyperinsulinemia was found in severe insulin-treated diabetics.

The Relationship Between Circulating Free and Bound Insulin, Insulin Antibodies, Insulin Dosage and Diabetic Control in Insulin Treated Diabetics

“…The wide variation in serum total insulin is similar to previous reports (Heding 1972;Rasmussen et al 1975); the values for circulating free insulin tended to be lower than in other series in which different methods were used (Lev-Ran 8c Ratt 1973;Heding 1969;Lev-Ran 1974;Lewis et al 1976). In the last two studies the patients were pregnant or post-partum.…”

“…The method of steady-state gel filtration has been used to measure serum free and bound insulin as it is less likely (Asplin et al 1977) to disturb their equilibrium than other methods (Lev-Ran 8c Ratt 1973;Heding 1969;Nakagawa et al 1973). …”

“…The influence of these antibodies on daily insulin dosage (Kerp et al 1968; Hum et al 1969) and on the quality of diabetic control (Dixon et al 1975;Andersen 1975) is controversial. The relative bio-availabilities of free and bound insulin is in dispute (Dixon et al 1975;Lev-Ran 8c Ratt 1973) as is the state of the circulating free insulin (Schlichtkrull et al 1971).In this paper we report measurements of serum free and bound insulin con¬ centrations and their relationships to insulin antibody binding characteristics and the prevailing blood glucose in one hundred long-term bovine insulin treated diabetics. We also attempt to relate these antibody characteristics to the quality of diabetic control and daily insulin dosage.…”

“…The influence of these antibodies on daily insulin dosage (Kerp et al 1968;Hum et al 1969) and on the quality of diabetic control (Dixon et al 1975;Andersen 1975) is controversial. The relative bio-availabilities of free and bound insulin is in dispute (Dixon et al 1975;Lev-Ran 8c Ratt 1973) as is the state of the circulating free insulin (Schlichtkrull et al 1971).…”