Spontaneous insulin fluctuations and the preabsorptive insulin response to food ingestion in humans.

Insulin secretion occurs in response to cephalic stimulation by foods; in humans, the response is quite variable and its importance in meal situations is difficult to assess. Insulinemia also varies spontaneously in the absence of food stimulation. In the present work, a comparative study of spontaneous and food-associated insulinemia changes was performed. Spontaneous preprandial fluctuations of glycemia and insulinemia were recorded and the presence of significant oscillations or trends was investigated. Premeal changes in insulinemia then served as a basis for evaluating the preabsorptive insulin response (PIR) during food ingestion. A sinewave fitted to preprandial insulin oscillations did not appear satisfactory as a basis for the assessment of the PIR. Significant PIRs were then defined in terms of deviation from a confidence interval (mean of the preprandial values +/- 2 SD). Significant PIRs were more frequent when the food presented was more palatable. Individual differences in responsiveness appeared. The physiological significance of a PIR over a background of spontaneous fluctuations is discussed.