Metabolic effects of pulsatile insulin infusion in the elderly

The present study investigated the metabolic effects of pulsatile insulin delivery at a pulse rate of 2 + 11 and 2 + 18 min in 7 healthy, elderly subjects (71.4 +/- 2.1 years), submitted to 260 min controlled iv glucose infusion via the Biostator. The endogenous secretion of pancreatic hormones was inhibited by somatostain (3 micrograms/min) and glucagon was replaced (67 ng/min) to basal levels. The same total insulin dose was delivered on both occasions. Insulin infusion rate was 1.3 and 2.0 mIU. kg-1. min-1 during switching on/off of 2 + 11 and 2 + 18 min, respectively. Blood glucose levels and glucose infusion rate were monitored continuously by the Biostator; [D-3-3H]glucose infusion allowed determination of glucose turnover. During the last 60 min of the experiment, pulsatile insulin at a pulse rate of 2 + 11 vs 2 + 18 min produced a stronger inhibition of endogenous glucose production, whereas glucose disappearance rate and glucose metabolic clearance rate were similarly affected. Plasma triglycerides, apolipoprotein B, and free fatty acids levels were also more suppressed during insulin delivery at pulse rate of 2 + 11 than at 2 + 18 min.