Oral sensory stimulation in men: effects on insulin, C-peptide, and catecholamines

To investigate the effect of oral sensory stimulation on cephalic phase insulin release (CPIR) and other compounds associated with glucose metabolism, a modified sham feed was used in which male subjects (n = 15) tasted, chewed, and then expectorated the food stimulus. Subjects remained fasted, sham fed, or ingested food on separate days over a 5-day period. After four baseline blood samples, poststimulus samples were taken every 2 min for 14 min and then every 15 min for 2.25 h. Increases in plasma insulin and C-peptide were found during the cephalic phase time period (0-10 min poststimulus) on the sham-fed and fed conditions when compared with fasted values. Glucose, norepinephrine, epinephrine, and free fatty acids were not affected by oral sensory stimulation or food ingestion during the cephalic phase period. The magnitude and profile of CPIR were similar after sham feeding and food ingestion. This study demonstrates that oral sensory stimulation can elicit CPIR in humans independently of changes in blood glucose.