SECRETORY RESPONSE AND ACTION OF INSULIN IN RELATION WITH OXIDATION OF PRIMARY NUTRIENT IN FEED-DEPRIVED SHEEP

Abstract

A hyperglycemic glucose technique (HGC) and an euglycemic glucose clamp technique (EGC) combined with the respiratory gaseous exchange measurement, respectively, were used to examine the effect of prolonged feed deprivation on insulin responsiveness to glucose stimulation and glucoregulatory effect of insulin in relation to with in vivo oxidation rates of carbohydrate, fat, and protein in sheep. The experiments were conducted in each sheep both after 12-h feed deprivation (Control) and 72-h feed deprivation. In both HGC and EGC experiments for feed-deprived sheep, the desired goals of glycemia were adjusted to those of control sheep. The feed deprivation decreased levels of blood glucose and insulin. The respiratory quotient value and heat production rate of sheep were decreased by feed deprivation. Insulin responsiveness to glucose was impaired in accordance with decreased tissue responsiveness to glucoregulatory effect in feed-deprived sheep. Feed deprivation induced increase in rate of fat oxidation and decrease in rate of carbohydrate oxidation. In the face of normoglycemia, feed deprivation induced lack in secretory response and action of insulin, and affected the shift in body metabolism more to non-carbohydrate.