Pulsatile insulin infusion and glucose-homeostasis in well-controlled type 1 (insulin-dependent) diabetic patients

Pulsatile, intravenous insulin infusion designed to mimic the portal insulin concentrations that emerge physiologically after a meal, has been postulated to improve glucose tolerance in Type 1 (insulin-dependent) diabetic patients. We studied the effects of insulin pulsing (10 i.v. pulses of human insulin of 0.035 U kg-1 idealised body weight were given, each of 20 s duration, with intervals of 6 min, three times per day covered with adequate administration of glucose) on 2 successive days on glucose-tolerance in nine well-controlled Type 1 diabetic patients on continuous subcutaneous insulin infusion therapy (age 26 (7) years, mean (SD); duration of diabetes 10 (7) years; body mass index 23.4 (2.3) kg m-2; HbA1c 6.0 (0.6)%). On the days before and after the insulin pulsing, the patients were subjected to metabolic assessments by an oral glucose tolerance test (1 g glucose kg-1 body weight) 30 min after the subcutaneous injection of 0.15 U kg-1 body weight regular human insulin and a subsequent bicycle-ergometer test. During these metabolic assessments, plasma free insulin concentrations, plasma glucagon and the non-protein respiratory quotient remained unaffected by the insulin pulsing. However, glucose tolerance deteriorated significantly (maximal glucose concentration 120 min after glucose load was 10.0 mmol l-1 before and 13.9 mmol l-1 after insulin pulsing, P less than 0.01). In conclusion, the pattern of insulin pulsing used in this study did not ameliorate oral glucose homeostasis in well-controlled Type 1 (insulin dependent) diabetic patients.