The Gut Talks First
Special cells in the intestinal lining sense a meal and release hormones within minutes.
Stop 1 of 8 on the Gut Line.
The digestive tract is the largest hormone-producing organ system most people never think about. Scattered through its lining are enteroendocrine cells. Each is a sensor: it tastes the contents of the gut and releases a peptide into the bloodstream.
Meal in, message out
After you eat, nutrients reach cells further along the intestine. Cells called L-cells respond by releasing GLP-1 (glucagon-like peptide-1) and PYY. Other cells release GIP and cholecystokinin. These are the incretin and satiety signals, and they arrive at several organs at once:
- The pancreas, where GLP-1 and GIP help the cells that make insulin respond when glucose is high.
- The stomach, where signals slow how quickly food leaves.
- The brain, where some of these messengers contribute to feeling full.
Short messages by design
Natural GLP-1 does not last. An enzyme called DPP-4 clips it, and its half-life in the blood is only a couple of minutes. This is a feature of the system: the signal should track the meal and then end.
Much of the later work on incretin-based medicines is about changing that. Some molecules are altered so the clipping enzyme cannot recognise them, and others are attached to carriers that slow clearance.
What is solid and what is still open
The existence of the incretin effect, where oral glucose triggers a larger insulin response than the same glucose given by vein, is well established. The relative importance of each signal, and how much of the sense of fullness comes from gut messengers compared with other routes, is still being worked out.
Why this stop sits next to Signal
Every message on this line is a peptide meeting a receptor. If receptors are new to you, go back to the first stop on the Signal Line before moving on.
End of this stop
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Education only, not medical advice. See the service notice.