From mouthwatering restaurant advertisements to snapshots of delicious meals on social media—it’s tough to ignore the enticing call of food. So when you reach for that snack, are you really hungry or simply unconsciously responding to the deluge of environmental signals?
For Yu Fu, Senior Principal Investigator at A*STAR’s Institute of Molecular and Cell Biology (IMCB), it could be the latter. “The role of the environment in driving overeating has been supported by multiple studies in humans and rodents, where the pairing of palatable food with environmental cues elicited excessive food intake,” he explained.
While environmental influences on excessive eating have been established, scientists have yet to pinpoint the precise neural circuitry that controls such behaviors. In search of answers, Fu and colleagues took a closer look at somatostatin neurons (TNSST), nerve cells located in the tuberal nucleus region of the brain, and their involvement in environmentally-driven feeding in mice.
Though foods rich in fat or sugar have previously been linked to environmentally-driven feeding, the team tried to stimulate the mice to consume excessive quantities even of their regular diet. They deliberately activated TNSST neurons in fed mice surrounded by regular chow in a certain environment, triggering them to eat despite not being hungry. Afterward, mere exposure to the same environmental context was enough to drive overeating, crucially demonstrating the TNSST neurons’ involvement in conditioning such behavior.
TNSST neurons are stimulated by a part of the brain called the ventral subiculum (vSub), which is involved in transmitting contextual information. Interestingly, the researchers found that impulse activity between vSub to TNSST neurons was elevated in conditioned mice. However, blocking these signals could reverse this effect, significantly reducing overeating in these mice.
“We showed a critical connection between the vSub and TNSST neurons that is not only necessary but also strengthened in environmentally-driven feeding,” Fu said, adding that the circuit works like an internal reward system that encourages overeating. For example, repeatedly indulging in sugary treats at work could make you more inclined to overeating in the office than at home.
Ultimately, their findings open up possibilities for regulating food intake based on overriding conditioned feeding responses. To this end, the team aims to visualize the brain-wide connectivity underlying environmentally-driven feeding to pinpoint how TNSST neurons differ from and fit in with other circuits. “This will provide novel neural circuitry targets that could have therapeutic potential against obesity and eating disorders,” said Fu.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Molecular and Cell Biology (IMCB) and the Singapore Bioimaging Consortium (SBIC).
