Korean researchers said Tuesday they have found a mechanism that stops animals from overeating, contributing to research on eating disorders and obesity prevention.

The research team, led by Professor Suh Seong-bae of the Biological Sciences Department at Korea Advanced Institute of Science and Technology (KAIST) and Professor Oh Yang-kyun at Neuroscience Institute of New York University Grossman School of Medicine, said they discovered two independent overeating suppression systems specifically found in fruit flies that were fed sufficiently.

When Suh worked for New York University in 2015 together with postdoctoral researcher Monica Dus, he found that Diuretic Hormone 44 (DH44+) neurons helped drosophila detect the concentration of sugar in the body and change behaviors to choose foods rich in nutrients.

Previously, researchers have reported nutrient sensors in the brain of mammals that regulate their activity. However, the latest study is the first to report the biological function of nutrient-sensing neurons.

Through a follow-up study, the research team discovered a higher regulatory signal that specifically inhibits DH44 neurons in the drosophila body in satiety conditions.

When DH44 neurons became operational, an inhibitory signal that is specifically activated when the fruit fly is full prevents overeating behavior, the research team found.

To check which peripheral organ sent the DH44 neuron inhibitory signal, the research team removed various peripheral organs connected to the fruit fly's brain one by one and traced the origin of the inhibitory signal.

The research team found that the signals were generated in the stomach/crop and ventral nerve cord (VNC).

The researchers also confirmed that DH44 neurons could recognize the signal of physical expansion caused by food intake through the “Piezo” channel by extending nerve branches to the internal organs of fruit flies. The piezo channel is a sensor that can detect the physical expansion of a specific cell or tissue. It plays an important role in the breathing and blood pressure control of mammals.

“Hugin” neurons in the VNC detect high nutrient concentrations and suppress the activity of DH44 neurons expressing Hugin receptors. The research team confirmed in an experiment that this mechanism could effectively block additional eating that burdens the digestive system when the body energy is already high.

The Piezo channel, activated by recognition of physical pressure on internal organs, and Hugin neurons, activated when many nutrients are circulating in the body, can suppress overeating caused by the activation of DH44 neurons, the research team said.

“The study was the first to show that higher signaling systems can specifically inhibit the feeding-inducing function of nutrient-sensing neurons in the brain of animals,” Suh said.

The results confirm the fact that overeating suppression is crucial for animal survival to the extent that it should be systematically done by synthesizing independently recognized physical and chemical measures, he said. “This study will help lay the foundation for research on human eating disorders and obesity prevention,” he added.

The study was published in the online edition of Neuron on May 19, with the title, “Periphery signals generated by Piezo-mediated stomach stretch and Neuromedin-mediated glucose load regulate the Drosophila brain nutrient sensor.”