Obesity affects 15% of adults in France and its different origins are not fully understood.
Normally, thanks to a specialized area of the brain (the hypothalamus), a person of normal weight will adapt his food intake according to his reserves and his needs. In contrast, in obese patients, this mechanism is defective. They suffer from binge eating. They cannot control their hunger and eat disproportionately. However, their levels of the hunger hormone, ghrelin, are normal or even low in these patients. Inserm researchers wanted to understand this paradoxical overeating.
Antibodies that disrupt hunger
Researchers have demonstrated the presence of specific antibodies in the blood of these obese patients. These immunoglobulins are used to recognize ghrelin and modulate appetite.
However, by binding to ghrelin, these immunoglobulins protect it from its rapid degradation in the circulation. Hormone hunger can then act longer on the brain and stimulate appetite.
Obese patients carrying these antibodies cannot therefore control their hunger and suffer from paradoxical overeating.
“Immunoglobulins have different properties in obese patients,” explains Sergei Fetissov, researcher at the Inserm unit in Rouen and main author of the study. They have a stronger “attraction” to ghrelin than those observed in subjects of normal weight or in patients with anorexia. It is this difference in “affinity” that allows immunoglobulins to transport more ghrelin to the brain and strengthen its stimulating action on food intake, ”he continues.
An experiment carried out on rats
To confirm this mechanism, the researchers conducted an experiment in rodents. Sergey Fetissov concludes that “when ghrelin was administered and associated with immunoglobulins extracted from the blood of obese patients, or with immunoglobulins obtained from genetically obese mice, it stimulated food intake more strongly. Conversely, when ghrelin was administered alone, or combined with immunoglobulins from non-obese people or mice, rodents regulated their appetite more by limiting their food intake ”.
“Our discovery opens a new avenue for designing treatments acting at the heart of this mechanism to reduce the overeating observed in the case of obesity, underlines Pierre Déchelotte, director of the Joint Inserm / University of Rouen Unit.
These results of this study are published in the scientific journal Nature Communications.
