Pulsatile Insulin Has Greater Hypoglycemic Effect Than Continuous Delivery

The relative hypoglycemic effects of pulsatile versus steadily infused insulin have been examined in six normal subjects in whom pancreatic insulin output was suppressed by somatostatin-14. Soluble insulin was infused continuously overnight on one occasion and on another occasion the same quantity was given in pulses of 2-min duration with a gap of 11 min. The mean plasma glucose concentrations were lower when pulsed insulin was given [mean for the last hour: 4.66 ± 0.08 mmol/L (±SEM) versus 5.53 ± 0.06 mmol/L (±SEM) for steady infusion], diverging significantly (P < 0.05 paired t test) 7 h after the start of the study. The specific binding of ¹²⁵I(A14)mono-iodo-insulin to monocytes was greater after pulsed insulin (2.9% with pulsed versus 2.4% with steadily infused insulin at tracer-only point; P < 0.02 paired t test). Thus, intravenous insulin has greater hypoglycemic effect when pulsed, possibly mediated by greater insulin receptor binding.