Researchers discover new brain mechanisms regulating body weight

Researchers from the University of Gothenburg, Sweden, have clarified the link between the molecule interleukin-6 (IL-6) in the brain and obesity. In experiments on rats and mice, they showed that the molecule had an effect on the risk of obesity and also on the points where this effect occurred in the brain.

Interleukin-6 (IL-6) is a well-known pro-inflammatory molecule and an essential part of the body's first line of defense during infection. Curiously, the brain can govern and use the IL-6 differently from the rest of the body. Researchers led by Karolina Skibicka's laboratory of the Sahlgrenska Academy in Sweden were wondering what happens to the brain levels of IL-6 after a diet leading to obesity.

Rats and mice were offered a tasty high-calorie food, a blend of fat and sugar, in addition to their usual low-calorie diet. Like many humans, rodents choose to eat too much when they come with high-calorie foods.

"What we discovered was that obese rats and mice had reduced IL-6, but only in a region of the brain called the lateral parabrachial nucleus (lPBN)," says Devesh Mishra, a postdoctoral fellow. . "To understand if this reduction of IL-6 is a good or a bad thing for the metabolic health of rodents, we have viro-genetically reduced the levels of IL-6 in lPBN very much." This has led to an increase in body weight and body fat, even in rodents fed a healthy diet. "

Therefore, the researchers concluded that reduced levels of IL-6 lPBN clogging in obesity are problematic and likely contribute to metabolic dysfunction and weight gain. Body weight is the result of the quantity of food consumed, that is to say, the energy intake, compared to the amount of energy used, that is to say the energy expenditure, the gain of weight can follow a dysfunction of one or other of these branches of the energy balance.

The study revealed that local IL-6 produced by a parabrachial nucleus is extremely important because it affects the two branches simultaneously: it decreases food intake and increases energy expenditure, the latter increasing the Brown fat activity, so that the body's energy is used to produce heat or fat burning. As a result, reduced levels of lPBN IL-6 disrupt the entire energy balance equation.

These results may be relevant not only for mice, but also for men, since an earlier study from the University of Gothenburg revealed an increase in blood serum IL-6 levels in obese and overweight men, then that levels of IL-6 in the brain measured in the cerebrospinal fluid are reduced.

There is an unresolved problem related to these findings: the researchers found that the reduction of IL-6 badociated with obesity was present only in men. Rats and female mice had normal levels of IL-6. Sahlgrenska's team is now studying why women are protected against IL-6-related dysfunction linked to obesity.

Given that obesity is a major global disorder with 1.9 billion people overweight, of whom 650 million are obese, effective anti-obesity treatments are essential to minimize the personal and medical burden of individuals and companies. On the scientific level, researchers believe that IL-6 as a mediating substance of satiety with brain region specificity is an important finding and that it can open new avenues in the search for strategies more effective fight against obesity.