Could Three Neurons Hold the Key to Appetite Control?
Zombies, robots, maybe mice: experts are increasingly finding complex behaviors controlled by surprisingly simple circuitry. A new study from Rockefeller University takes this concept to a new level by demonstrating that a circuit made up of just three types of neurons in mice might be the key to regulating appetite.
Surprising Simplicity in a Complex Behavior
Food cravings, complicated eating habits, and the constant battle with our waistlines – eating behavior seems like a complex, multi-faceted process. Surprisingly, new research suggests a simple network of just three types of neurons in the brain of mice plays a crucial role in controlling this complex behavior. The discovery, published in the journal
, has significant implications for understanding obesity and potentially developing new weight management strategies.
A Circuit Called BDNF
“It’s surprising that these neurons are so keyed to motor control,” says Christin Kosse, a neuroscientist at Rockefeller University. “We didn’t expect that limiting physical jaw motion could act as a kind of appetite suppressant.”
The researchers focused on a particular neuron population called BDNF neurons located in the ventromedial hypothalamus (VMH), a brain region already known to be involved in appetite regulation. Previous studies had shown that disruptions to BDNF expression in this area were linked to metabolism, overeating, and obesity.
Chewing, Leptin, and Appetite Control
Using optogenetics, a revolutionary technique that allows scientists to switch brain activity on and off with light, the researchers activated BDNF neurons in some mice. The result? The rodents lost virtually all interest in food, regardless of whether they were full or hungry. Even a tempting fatty, sugary treat failed to pique their interest.
“This was initially a perplexing finding, because prior studies have suggested that this ‘hedonic’ drive to eat for pleasure is quite different from the hunger drive, which is an attempt to suppress the negative feeling, or negative valence, associated with hunger by eating,” explains Kosse. “We demonstrated that activating BDNF neurons can suppress both drives.”
The key to understanding this seemingly paradoxical effect may lie in the way BDNF neurons receive input. They gather information about the body’s state from sensory neurons, including those responsible for signaling hunger. Leptin, a hormone known to regulate appetite, plays a crucial role in this communication.
The BDNF neurons then relay this information to the pMe5 motor neurons, which are responsible for controlling jaw movements. Interestingly, inhibiting the BDNF neural circuit caused the opposite effect: the mice chewed incessantly, even gnawing on indigestible objects.
Implications for Obesity and Beyond
This unique circuit shines a light on how the brain orchestrates the complex interplay between our sensory experiences, feelings of hunger, and motor control. The researchers believe that damage to the VMH, which houses the BDNF neurons, may explain why some individuals struggle with obesity.
“The evidence presented in our paper shows that the obesity associated with these lesions is a result of a loss of these BDNF neurons, and the findings unify the known mutations that cause obesity into a relatively coherent circuit,” says Rockefeller University molecular geneticist Jeffrey Friedman.
This research emphasizes that the line between reflex and deliberate behavior may be blurrier than we thought. It ultimately opens new avenues for understanding and potentially treating appetite disorders and obesity.
**Learn more about this groundbreaking research at Rockefeller University’s website.**