[The cephalic phase of insulin secretion]

Abstract

Human studies had suggested that the cephalic phase of digestion induced a cephalic phase of insulin secretion. A detailed study of the intensity and time course of the phenomenon was performed in the free feeding rat and confirmed in other mammals. This secretion is reflexly triggered by food-related sensory stimuli and is vagally mediated. Anatomical, neurochemical electrophysiological and behavioural studies, showed that the reflex might be organized at the brain stem level receiving major modulation influences from the hypothalamus. The cephalic phase of insulin release is a conditioned reflex. One consequence of that early secretion is to damp down the important variations in the levels of circulating metabolites following absorption. The relationships between the amplitude of the cephalic phase insulin response and the basal insulin level on the one hand, the nutritional composition of the ingested food on the other, are still not clear. Some evidence exists that palatability, meal size and the amplitude of the cephalic phase insulin secretion are linked. This could be a possible etiology in some cases of nutritional obesity.