hD2R neurons:

can Brain Cells Beat Obesity?

A recent study done on mice shows that brain cells not only help regulate memory, but can influence the body’s ability to restrain from eating when it is not beneficial. A natural mechanism in the brain that can curb the impulse to eat may be just the answer to reducing the prevalence of overweight and obesity.

The brain, food and hD2R neurons

Eating has always been considered an instinct in animals for reasons of survival. The sight and smell of food normally triggers the desire to eat without intervention from the brain. Yet recent research shows that animals have complex mental processes that affect their decisions to eat or not to eat in a given moment. Researchers at the Rockefeller University in New York City studied a group of neurons, or brain cells, and their effect on feeding behavior in mice. The results were published in the journal Neuron and the interesting discovery was that food intake is actually reduced when these brain cells are activated.

The study focused on dopamine 2 receptor (hD2R) neurons located in the hippocampus, a part of the brain that plays a role in the formation of memories and the regulation of emotions. Research has confirmed that these neurons are also a part of the complex brain circuitry that regulates eating. Estefania P. Azevedo, the author of the study and a postdoctoral researcher in the Laboratory of Molecular Genetics at Rockefeller University, explains, “These cells keep an animal from overeating. They appear to make eating less rewarding and, in that sense, are tuning the animal’s relationship to food”. In fact, when these neurons were stimulated, the mice ate less; when the neurons were silenced, the mice ate more.

How does this research help curb overeating?

Animals cannot eat if they do not know where to find food. To find out how hD2R neurons influence an animal’s memory of a food location, researchers stimulated the mice’s brain while the animals explored an environment full of food. When the neurons were stimulated, the mice returned less often to locations they had previously found food in. This suggests that neuron stimulation weakens memories related to meals and food location and, thus, stops an animal from going back for more food. It’s like switching the hunger switch on and off. Azevedo gives an interesting explanation for these findings, “Mental connections between food and location are important for survival, and the strength of these connections is regulated by how rewarding an experience is. Because hD2R neurons affect an animal’s relationship with food, it also ends up affecting these connections”. Even though animals need to eat and normally benefit from eating, there are some circumstances in which eating may not be so beneficial. For example, if an animal has already eaten and is full, hunting for more food is unnecessary and risky as they unduly expose themselves to predators. Interestingly, these neurons seem to restrain animals from eating or wanting to eat when it is not beneficial.

The team also investigated how hD2R neurons link to other brain circuits and found that neurons can receive messages from certain parts of the brain and send messages to another area that influences feeding behavior. The researchers concluded that the brain can influence the appetite and curb eating by controlling memories related to eating.

Using science to combat overweight and obesity

Overweight and obesity are responsible for major health problems. Data from the World Health Organization (WHO) shows the number of people worldwide suffering from obesity has tripled since 1975 and, according to the National Institutes of Health, obesity and overweight together are the second leading cause of preventable death in the United States. There are many factors that have contributed to a worldwide tendency towards weight gain, including sedentary lifestyles and jobs as well as an increase in the consumption of high-fat, processed foods.

Treatment for overweight and obesity has normally focused on favoring healthier lifestyles and eating habits in order to lose weight. In extreme cases, even medication and surgery are used. This new research gives us a better understanding of how the brain controls the impulse to eat and may offer insight on improved treatments in the future. “Our study shows that brain areas involved in cognitive processing and memory formation affect feeding behavior,” says Azevedo. “So, it is possible that, with training, people may be able to learn to change their relationship to food.”

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