The role of the ileum in the control of food intake and intestinal adaptation

Abstract

Studies on animals that drastically reduce their food intake after having a jejunoileal bypass or an ileal transposition surgery suggest that the lower ileum may play a major role in the control of daily food intake. In this study, eight rats were given slow continuous infusions of either 18, 28, or 38 mL of their normal liquid diet directly into their upper ileum. They reduced their daily intake in a compensatory way for the two smaller infusions and in a more than compensatory way for the large infusion. The later results suggests that the large infusion may have caused the rats some discomfort, which led to a lower food intake. This was tested in a conditioned aversion paradigm with an ileal infusion of 26 mL of the diet into eight naive rats. These rats showed a strong aversion to the ileal infusion. Infusion of the same amount of diet into the stomach of eight other rats failed to demonstrate an aversion and showed that the procedures of the experiment did not produce the aversion. The infusion of relatively small amounts of liquid diet into the ileum produces an internal signal that reduces intake and is regulatory. A second process in which ileal infusion causes discomfort leads eventually to a more than regulatory decrease in daily intake.