Insulin responsiveness to glucose and tissue responsiveness to insulin over the feeding cycle in sheep

Insulin responsiveness to glucose and tissue responsiveness to insulin, using the hyperglycemic clamp and the hyperinsulinemic euglycemic clamp techniques, were measured before, during and after feeding in sheep fed an alfalfa hay and commercial concentrate diet. Glucose infusion rate and the plasma insulin increment in the hyperglycemic clamp experiment were higher during the feeding period (0 to 1 h after initiating feeding) than during the pre- and post-feeding periods. The ratio of plasma insulin increment to glucose infusion rate remained unchanged over the feeding cycle. Only a slight increase (P less than .05) in the glucose infusion rate was observed during feeding in the hyperinsulinemic euglycemic clamp experiment. These results suggest that insulin responsiveness to glucose tends to be enhanced during the feeding period but that tissue responsiveness to insulin is not changed over the feeding cycle in sheep.