You always have room for sweet treats
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Even after eating a large meal, most people still find room for sweets. Currently, mouse studies show that neurons that cause fulfillment are also responsible for sugar cravings. In other words, there appears to be a neurological basis for our love for dessert.
Previous studies have shown that naturally occurring opioids in the brain play an important role in sugar cravings. The main producers of these opioids are neurons located in the brain region that regulates appetite, metabolism and hormones called the arcuate nucleus of the hypothalamus. These cells, known as proopiomeranocortin (POMC) neurons, also control the feeling of fullness after eating.
To understand whether cells play a role in sugar cravings, Henning Fencerau The Max Planck Institute for Metabolism Research in Germany and his colleagues tracked the opioid signals POMC cells send to the brain. They did so by bathing brain slices from three mice with a fluorescent solution that binds to the receptors of these opioids.
The brain regions with the highest density of these receptors were the paraventricular nuclei of the thalamus (PVT), known to regulate breastfeeding and other behaviors. It suggested that sugar craving was associated with communication between these two brain regions – arcuate nuclei and PVT of the hypothalamus.
Therefore, researchers monitored the activity of neurons in these regions when mice were eating regular food. After 90 minutes the animals looked full – they only bite into additional food. At that point, the team gave them a sugar-like butterfly dessert.
On average, neuronal activity between brain regions was nearly quadrupled during the time of dessert, compared to when eating a normal diet. Spikes begin before they start eating sweets, suggesting that this brain pathway determines sugar cravings.
Researchers confirmed this using a technique called optogenetics, which turns cells on and off with light. Inhibiting the signal from POMC neurons to PVTs led to mice consumed 40% less dessert.
“Cell types that are very well known for driving satiety also emit signals that cause sugar appetite, especially when they are full,” says Fencelau. “This would explain why animals-humans over-impose sugar when they actually fill up.”
I don’t know why this pathway evolved in animals. It may be because sugar is more likely to be more energy than other sources such as fat and protein, says Fencelau. So eating dessert is like refilling a gas tank.
He hopes that the study could lead to new treatments for obesity, but he acknowledges that hunger and craving are complicated in everyday life. “There are so many other pathways in the brain that of course you can disable this. We found this pathway, but how it plays with many others. That’s something we don’t know at this point.”
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Source: www.newscientist.com
