Lipids (fat) would act as a drug for the brain
Focus today on a press release2from the CNRS whose title is as follows: “Obesity: lipids, hard drugs for the brain?”
It was in Paris that Serge Luquet made a really interesting observation for research by highlighting the fact that triglycerides (fats) were aregulator of the feeling of rewardwithin the brain itself.
An observation published this Tuesday, April 15 in the magazine Molecular Psychiatry1
To understand the experience
Our brain has a reward circuit, mainly constituted by what is calledthe mesolimbic circuit. When this circuit is stimulated, then chemical compounds enhance the satisfaction and reward effect in humans. It is this circuit that is strongly stimulated when taking drugs, thus modifying its sensitivity in order to regulate the craving (ever more important)3.
The CNRS wondered because this structure of the mesolimbic circuit includes an enzyme (a kind of small catalyst) that has the particularity of being able todestroy fat, and more precisely triglycerides (which are lipids from, in particular, food).
Why would such an enzyme be located in this specific regionof reward when the brain mainly consumes only glucose?
Experiences and results
To answer this question, the CNRS “Functional and Adaptive Biology” laboratory (directed by Serge Luquet) used mice that have brains similar to that of humans and are by default more attracted to high-fat food than to “classic” food.
A first experiment consisted in injecting mice with triglycerides directly into the brain (via the carotid artery), and measuring their effects. This simulation of a “good meal” greatly reduces the animal’s motivation to make efforts to get a treat (in addition to halving its physical activity). Mice that were infused in this way even had a balanced diet between the two choices offered to them: fat diet, and normal diet.
»In summary, a mouse that receives fat directly to the brain is less motivated by treats and provides less physical effort. She seems satisfied.
A second experiment consisted in injecting mice with these triglycerides, but having previously destroyed the enzyme necessary to destroy this fat in the brain. In this case, triglycerides pass into the brain but are therefore not detected (because the enzyme no longer exists). In this case, the mice are extremely motivated by treats and orient themselves almost exclusively towards this food source.
In summary, a mouse that receives fat directly to the brain, but is not able to consume it, remains highly motivated by the treats and exerts a lot of physical effort to achieve it. She doesn’t seem satisfied.
The behavior of mice is therefore strongly influenced by the consumption, or not, of triglycerides.
Other experiments have been carried out over longer periods of time, with eloquent results.
» Over long injection periods, the organism of the mice adapts and needs more fat to be fully satisfiedtag. However, the mice continue to provide less physical effort.
In conclusion, triglycerides therefore have a real effect on the reward circuit within the brain. This is a similarity with the consumption of drugs.
Link to obesity in humans
In humans, the fact of eating obviously does not respond to a single biological constraint: eating is generally a pleasure. It is in this sense that the fact that lipids are associated with the reward circuit, constitutes a real parallel with hard drugs.
Several cases of severe obesity show an overconsumption of fatty foods. This could be explained, in part, by the fact that the individual needs more fat to “be rewarded by his brain”. A behavior that is often paradoxical because if triglycerides modify the reward circuit, so that more fat is now needed, these also reduce the desire to do physical activity. But a sedentary lifestyle and the overconsumption of fatty foods are obviously conducive to overweight and obesity.
Be careful however, triglycerides are obviously essential to our body and our vitality. It is in excessive quantity that the risk is present.
Interestingly, another study published in February already suggested that this reward circuit was involved in notions of obesity4.
Stephen Paul is the lead author and founder of My Health Sponsor. Holder of a diploma in health and well-being coaching with more than 200 articles in the field of health, he makes it a point of honor to offer advice based on reliable information, based on scientific research, and verified by health professionals.