Plasma free fatty acid turnover during insulin-induced hypoglycemia

Abstract

Plasma free fatty acid (FFA) concentration falls when an infusion of glucagon-free insulin is initiated in the normal unanesthetized dog in the postabsorptive state. Using C 14 palmitate it was shown that the lowered FFA concentration is caused by decreased FFA production. This decreased FFA production accompanies increased glucose uptake by the tissues as demonstrated using C 14 glucose. During slow insulin infusion, when plasma glucose concentration remains above 75 mg%, FFA production and concentration remain low. However, during more rapid insulin infusion, when plasma glucose concentration falls below 50 mg%, the initially lowered FFA production rebounds and FFA production and concentration exceed the preinsulin level. Glucose uptake always remains elevated during insulin infusion. Dibenzyline or guanethidine pretreatment blocks the rebound in FFA production. Thus decreased FFA production, due presumably to decreased FFA release by adipose tissue because of insulin-stimulated glucose uptake, can be overpowered by a sympatho-adrenal response to hypoglycemia during a continued infusion of insulin and a resulting continued increased glucose uptake.