Insulin clearance from plasma in type I (insulin-dependent) diabetic patients: influence of glycaemic level

The influence of the actual glycaemic level on the kinetics of insulin disappearance from plasma was studied in 16 type I diabetic patients. Constant intravenous infusion of insulin (1-5 mU.kg-1.min.-1) was used to achieve different levels of steady state plasma free insulin concentrations, while the blood glucose level was clamped at normoglycaemia, 4.1 +/- 0.1 mmol/l (mean +/- S.E.M.), and mild hyperglycaemia, 8.2 +/- 0.1 mmol/l. The experimentally determined data were compared using a previously validated model of first order kinetics for insulin disappearance from plasma in diabetic patients. At the physiological insulin concentration range the median clearance rate of insulin was 23 ml.kg-1.min-1 (range 16-26) at normoglycaemia and 23 ml.kg-1.min-1 (19-35) at hyperglycaemia (P = 0.45). At supraphysiological levels, insulin was cleared at a lower rate at normoglycaemia than at hyperglycaemia. No correlation was observed between the insulin clearance rate and the duration of diabetes or the haemoglobin A1C level (both Spearman's rho = 0.08). In conclusion, the insulin clearance rate from plasma is independent of the actual glycaemic level and hardly influenced by the long-term glycaemic level in type I diabetic patients.