Nature sub-journal: Activation of a group of neurons in the amygdala leads to overeating

As we all know, delicious foods are usually those that are high in sugar, fat, and calories (better palatability).

While they satisfy our appetite, they also lead to an imbalance in the body's energy homeostasis, bringing more and more obese people
to the world.
Today, obesity is a global epidemic, and many major life-threatening diseases are related
to obesity.

While poor dietary choices (not keeping your mouth shut) and lack of exercise (not opening our legs) are the main causes of obesity, how our food preferences are established remains an open question
.
At the moment, choice seems to be more important
than effort for weight loss.

The amygdala is one of the important brain regions, named
for its almond-shaped shape.
The amygdala plays a major role in memory processing, decision making, and emotional responses, including fear, anxiety, and aggression, and it is considered part of the
limbic system.
So, what does the amygdala have to do with food choices?

Like most people, mice are fond of high-sugar and high-fat foods
.
They can even choose between
"Bad" or "Food".

In a new study published in Nature Neuroscience, a team led by Cold Spring Harbor Laboratory (CSHL) identified a previously uncharacterized group of single neurons in the amygdala that plays a key role in promoting metabolic responses through behavioral changes: this group of neurons drives mice to choose high-sugar or high-fat foods after a full meal, triggering "hedonistic" overeating and eventually obesity
.
From a therapeutic perspective, targeting this group of neurons leads to long-term weight loss and improved
metabolic health.
The study notes that the amygdala is an ideal entry point
to unravel the complex metabolic regulatory circuits of the brain under energy homeostasis.

The interstitial nucleus of the anterior combosis hindlimb (IPAC) is a major structure
that expands the amygdala.
IPAC neurons are activated
by innate or acquired taste stimuli.
They receive dense projections
from the insular cortex, a hedonic hot spot.
However, until now, the role of IPAC in energy homeostasis is unknown
.

In the new study, the team revealed through mouse experiments that neurotensin-expressing neurotensins in IPAC play a key role
in establishing dietary choices and coordinating behaviors that affect metabolic health.
They found that IPAC-Nts, which expresses neurotensin, encodes dietary preferences for unhealthy, energy-dense foods (such as foods high in fat and sugar).

In experiments, mice stop eating because they are full; But when the researchers used optogenetics to activate the IPAC-Nts neurons of mice, the already full animals would restart a new round of eating behavior, that is, hedonic eating behavior; The activated IPAC-Nts also modulated food preferences, making mice more willing to choose foods high in sugar and fat
.

In contrast, after the IPAC-Nts neurons were acutely inhibited, the mice were no longer attracted to the high-sugar, high-fat foods that had previously tempted them, that is, reduced hedonic eating
.
At the same time, chronic inactivation of IPAC-Nts neurons also reduced taste preference in mice, also enhanced exercise and energy expenditure, and showed long-term weight loss and metabolic health improvements
.

Together, the study revealed that the activity of individual neuronal populations can regulate energy homeostasis
bidirectionally.
Usually, on the road to weight loss, few people can control their weight
for a long time.
Over time, the body's metabolic processes reverse all previous weight loss gains
.
The group of neurons that control diet identified in the new study offers promising targets for developing new strategies to prevent and treat obesity
.

The team says deeper characterization of this brain region could reveal molecular heterogeneity
that its neurons have not yet discovered.