Treatment with insulin lispro changes the insulin profile but does not affect the plasma concentrations of IGF-I and IGFBP-1 in type 1 diabetes

OBJECTIVE IGF-I levels in patients with type 1 diabetes without endogenous insulin production are low. Our aim was to examine whether the plasma insulin profile obtained by treatment with the insulin analogue lispro has a different effect on plasma concentrations of IGF-I and IGFBP-1 than that seen during treatment with conventional human insulin (regular insulin). DESIGN AND PATIENTS Twelve patients with type 1 diabetes, age 47.8 +/- 2.4 years (mean SEM), body mass index 26.5 +/- 1.0 kg/m(2), diabetes duration 30.5 +/- 3.2 years participated in this open label randomized cross-over study. IGF-I and IGFBP-1 levels were measured at the end of 6 weeks treatment with each insulin being administered by a continuous subcutaneous insulin infusion. IGF-I was measured fasting while IGFBP-1, free insulin and blood glucose were measured fasting and repeatedly after a morning meal preceded by an insulin bolus dose. RESULTS Lispro gave a marked insulin peak of 135 +/- 20 pmol/l 50 minutes after injection. After an initial rapid rise, human regular insulin reached a plateau of approximately 50 pmol/l. The plasma free insulin area under the curve (AUC) from 0710 h to 0910 h was more than twice as large on lispro as on regular insulin (P = 0.01). Plasma IGF-I concentration was 78.8 +/- 10.9 mug/l on lispro and 82.3 +/- 10.5 mug/l on human regular insulin (not significant). AUC for IGFBP-1 did not show a significant difference even when divided from 0710 h to 0910 h and from 0930 h to 1430 h. Blood glucose AUC after administration of the bolus was significantly lower during treatment with lispro (P = 0.006) but glycosylated haemoglobin (HbA1c) was 6.4 +/- 0.2% on both therapies. CONCLUSIONS Our results indicate that the effect of lispro on IGF-I and IGFBP-1 in patients with type 1 diabetes does not differ from that of human regular insulin.