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A family eating fast food in a food court. Image © Tim Sandle.
With many of us, eating too quickly overcomes the normal feelings of being sated and the biological signals from our stomach to our brains keeps us from eating so much that we end up regretting it later. What appears to pull us back from over-eating, in many cases, are our tastebuds.
A biological insight has shown, based on brainstem recording, how our tastebuds are the first line of defence against eating too fast. This new understanding could lead to new avenues for tackling weight loss.
University of California – San Francisco researchers demonstrated this by stimulating the perception of flavour to pinpoint a set of neurons that function to curtail our food intake.
According to lead researcher Zachary Knight the results could be significant: “We’ve uncovered a logic the brainstem uses to control how fast and how much we eat, using two different kinds of signals, one coming from the mouth, and one coming much later from the gut. This discovery gives us a new framework to understand how we control our eating.”
Using an animal model, the researchers used imaging and recording to reveal the brainstem structure critical for feeling full. This is termed the nucleus of the solitary tract, or NTS.
It was demonstrated that when food is put directly into a mouse’s stomach, brain cells called PRLH (for prolactin-releasing hormone) are activated by nutrient signals sent from the GI tract.
When the scientists allowed the mice to eat the food as they normally would, those signals from the gut did not show up. Instead, the PRLH brain cells switched to a new activity pattern that was entirely controlled by signals from the mouth. The activity of the PRLH neurons seems to affect how palatable the mice found the food.
This meant these cells are activated by the perception of taste. Hence there are other components of the appetite-control system that researchers need to think about.
Here, a PRLH-neuron-induced slowdown could be the solution. The taste of food triggers these neurons to switch their activity in seconds, from keeping tabs on the gut to responding to signals from the mouth.
The research appears in the journal Nature, titled “Sequential appetite suppression by oral and visceral feedback to the brainstem.”
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