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Hunger On/Off Switch Could One Day Help People With Obesity, Eating Disorders

eating
By activating or deactivating cells in certain parts of the brain, scientists were able to control when mice would become hungry. Leonid Mamchenkov, CC BY 2.0

Ending obesity would be so easy if we could just turn off the switch in our brains that said eat more, or on the other hand, if anorexics could just turn on that switch. Right? Well we just got one step closer to making that a reality, because scientists have now pinpointed the groups of cells that cause people to eat and to stop eating, and developed a so-called on/off switch with which they were able to control the eating habits in mice.

“This is a really important missing piece of the puzzle,” Seth Blackshaw, a neuroscientist at Johns Hopkins University, told Science News. “These are cell types that weren’t even predicted to exist.”

But they were indeed real, and they were located in a part of the brain known as the bed nucleus stria terminalis (BNST), in which some neuronal fibers stretch to the part of the brain known for its association with hunger, the lateral hypothalamus. Scientists at the University of North Carolina, Chapel Hill, managed to genetically modify the cells to respond to laser light — they would either shut down or send off messages.

As expected, the genetic modification worked, and when the researchers activated the BNST neurons, the mice ate, without stopping, even when they became full. “As soon as you turn it on, they start eating and they don’t stop until you turn it off,” Garret Stuber, co-author of the study, told Science News. Conversely, mice that were modified to have BNST neurons shut down in response to light stopped eating for the entire time that the light was on.

The experiments showed that activating BNST neurons, which made the mice eat, led neurons in the lateral hypothalamus to shut down. This meant that lower levels of activity in the lateral hypothalamus was responsible for overeating, the researchers said — they had previously thought that these cells encouraged eating.

Although the researchers don’t know how long the mice would have continued to eat or starve, since their experiments only last 20 minutes, they still believe the findings could eventually be used to help people who are obese or have eating disorders.

People with eating disorders could either eat too much or not enough. Anorexia nervosa is a disorder in which people don’t eat nearly enough food. It’s just as much a physical condition as a psychological one, since many anorexics believe they are overweight. People with this disorder could be as much as 15 percent below the normal weight for a person of their size.

Obesity, and binge eating — out of control eating — are disorders that go the opposite way. About one third of Americans are obese, and binge eating is partially accountable. Research has suggested that obese people may continue to eat excessively because the nerves inside of their stomach can’t sense when they’re full anymore. For these reasons, an “on/off” switch that can control how people eat could be a positive development.

Source: Stuber G, Ung R, Jennings J, et al. The inhibitory circuit architecture of the lateral hypothalamus orchestrates feeding. Science. 2013. 

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