New research has revealed intriguing insights into the neuroscience behind sugar cravings, even after consuming a substantial meal. Findings from a study on mice indicate that the neurons responsible for feelings of fullness are also linked to the urge for sugary treats. This suggests a neurological foundation for the widespread desire for dessert.
Prior investigations highlighted the role of naturally occurring opioids in the brain in driving sugar cravings. These opioids are primarily produced by pro-opiomelanocortin (POMC) neurons, located in the arcuate nucleus of the hypothalamus, a region that regulates appetite, metabolism, and hormones. Notably, these neurons also play a critical role in signaling satiety after eating.
To explore the connection between POMC neurons and sugar cravings, researchers studied the opioid signals emitted by these cells. They exposed brain slices from mice to a fluorescent solution that binds to opioid receptors. The area with the highest density of these receptors was identified as the paraventricular nucleus of the thalamus (PVT), which is known to influence feeding behaviors. This discovery indicated that the craving for sugar might be linked to communication between the arcuate nucleus of the hypothalamus and the PVT.
During the experiment, the activity of neurons in these regions was observed as the mice fed on their regular diet. After 90 minutes, when the mice appeared full, they were offered a sugary treat. Remarkably, neuronal activity surged fourfold in the brain regions as the mice indulged in the dessert, even before they began eating it. This spike points to the idea that this particular brain pathway is pivotal in driving sugar cravings.
Using optogenetics, a method that allows researchers to control neuronal activity with light, the team inhibited signals from POMC neurons to the PVT. As a result, the mice consumed 40% less sugar, confirming the link between these neurons and sugar appetite.
“Cells that are well-known for inducing feelings of fullness also release signals that drive sugar cravings, especially when the subject is at a state of satiety,” explained Fenselau. “This may illustrate why humans often overindulge in sugary foods, even when they’re full.”
The evolutionary purpose of this pathway remains unclear, though it may be tied to the fact that sugar is a quick source of energy, more easily metabolized than fats or proteins. Consuming sugar might be akin to topping off an energy reserve.
Fenselau hopes the findings will inform future obesity treatments, while acknowledging the complexity of hunger and cravings. “Numerous other pathways in the brain can influence these behaviors, and while we have identified this pathway, understanding its interaction with others requires further research.”
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