Infusion of lipid into the ileum slows gastric emptying and reduces appetite. The hormone chiefly responsible for this 'ileal brake' is:
- A Motilin, released cyclically from the upper small intestine during fasting
- B Gastrin, released from antral G cells in response to peptides
- C Peptide YY, released from ileal and colonic L cells in proportion to luminal fat, slowing gastric emptying and increasing satiety ✓
- D Secretin, released from duodenal S cells in response to acid
Correct answer: C. Peptide YY, released from ileal and colonic L cells in proportion to luminal fat, slowing gastric emptying and increasing satiety
Explanation
Peptide YY is released from L cells of the ileum and colon when fatty chyme arrives, and it feeds back to slow gastric emptying, slow intestinal transit and promote satiety via hypothalamic Y2 receptors. This feedback prevents the distal gut from being overloaded with undigested nutrients. Motilin governs fasting migrating motor complexes rather than postprandial braking, and secretin responds to acid, not fat, which eliminates options A and D.
Reference: Ganong's Review of Medical Physiology, 26th ed.
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