To find the cause of the “dessert stomach”, the researchers investigated the reaction of mice to sugar and discovered that completely satiated mice still ate desserts. The brain investigations showed that a group of nerve cells, the so -called POMC neurons, are responsible for this. These neurons become active as soon as mice received access to sugar, which facilitated their appetite.
When the mice are full and eat sugar, these nerve cells not only release signaling molecas that stimulate satiety, but also one of the body opioids: ß-endorphine. This acts on other nerve cells with opioid receptors and triggers a sense of reward, which makes mice eat sugar even beyond fullness. This opioid route in the brain was activated specifically when mice ate additional sugar, but not when they ate normal or fatty foods. When the researchers blocked this route, the mice refrained from eating additional sugar. This effect was only observed in complete animals. In hungry mice, the inhibition of the release of ß-endorphin had no effect.
Interestingly, this mechanism was already activated when the mice perceived sugar before eating it. In addition, opioid was also released in the brain of mice that had never eaten sugar before. As soon as the first sugar solution entered the mouths of the mice, ß-endorphine was released in the “dessert stomach region”, which was further strengthened by additional sugar consumption.
What happens in humans?
The scientists also carried out brain scanns in volunteers who received a sugar solution through a tube. They discovered that the same region of the brain reacted to sugar in humans. In this region, as in mice, there are many opioid receptors near satiety neurons.
“From an evolutionary perspective, this makes sense: sugar is rare, but provides fast energy. The brain is scheduled to control sugar intake whenever it is available,” explains Henning Fenselau, leader of the Research Group of the Max Institute Planck for metabolism research and head of the study.
Relevance for the treatment of obesity
The findings of the research group could also be important for the treatment of obesity. “There are already medications that block opioid receptors in the brain, but weight loss is less than with suppressor appetite injections. We believe that a combination with them or other therapies could be very useful. However, we need to investigate this more thoroughly. “says Fenselau.