Feeling full and feeling sick run on different brain wires, mouse study finds

The question

GLP-1 drugs make people eat less, but many also feel nauseous, especially early on. Is that the same effect, so feeling full is just a mild form of feeling sick? Or are they separate?

What the team found

Working in mice, the researchers looked at the hindbrain, an area at the base of the brain that receives signals from the gut. They found neurons carrying the GLP-1 receptor in two neighbouring regions.

When they switched on one group, mice ate less and showed normal signs of being full. When they switched on the other, mice also ate less, but they avoided flavours paired with the activation, a standard sign of nausea in rodents. Blocking each group separately removed one effect while leaving the other.

Why it matters

If the two effects use different wiring in people too, it may be possible to design drugs that reach the fullness neurons more than the nausea ones, or to pair GLP-1 drugs with something that quiets the aversion pathway. Several groups are working on both ideas.

The limits

Mouse brains are a model. Human nausea is reported, not inferred from flavour avoidance, and the hindbrain is only one of the places GLP-1 drugs act. The study maps a mechanism; it does not show that a nausea-free drug is close.

Source Huang K.-P. et al., Nature, 2024

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