Researchers from Toulouse have studied how to activate heat production by brown adipose tissue, which unlike white mass, does not store but burns fat.
- Unlike white adipose tissue, which stores fat, brown adipose tissue burns them to generate heat and regulate body temperature.
- Exposed to cold and in the absence of food, mice not expressing two enzymes (ATGL and HSL) in triglycerides (fatty acids) are not able to maintain their body temperature.
- Using advanced imaging techniques, the Toulouse team observed that the ability of brown fat to produce heat was greatly reduced in rodents that did not have the enzymes.
The majority in the body, white adipose tissue stores fat and is responsible for obesity and its complications in the event of excess. Conversely, brown adipose tissue, which represents only a few percent of fat mass, exhibits the ability to use fatty acids to generate heat, which helps maintain body temperature. “We have to understand how it works and how we are going to be able to reactivate it. And to be able to reactivate it, we have to understand how it works,” declared, to the news site Tell them!Dominique Langin, university professor, hospital practitioner at the University of Toulouse III – Paul Sabatier and researcher at the Institute of Metabolic and Cardiovascular Diseases (I2MC, Inserm/UT3).
Obesity: creating mice lacking two enzymes in triglycerides
In a recent study, published in the journal Cell Metabolismhe thus, with his team, wanted to determine the activation pathway of brown fat cells, which are made up of triglycerides, a combination of three fatty acids linked to a glycerol molecule. “Hydrolysis (i.e. the destruction of a chemical substance by water) of triglycerides is carried out by two enzymes: adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL).” To carry out the work, the scientists created mice that expressed neither enzyme in brown adipose tissue. Then the animals were exposed to cold and deprived of food.
Brown fat in rodents is hypertrophied and does not regulate body temperature
According to the results, the brown fat of these rodents was hypertrophied, “with increased lipid droplet size and preserved mitochondrial surface area and density.” Maintaining body temperature during cold exposure was compromised in mice lacking functional ATGL and HSL enzymes in the fasted state but not during the feeding period. “Positron emission tomography shows that cold-induced oxidative activity of brown adipose tissue is greatly reduced and fatty acid metabolism is impaired in created animals,” can we read in the study.
Weight loss: “molecules” to “activate” the production of heat by brown fat
Thus, the data show that intracellular lipolysis, that is to say the breakdown of fats in brown tissue, is necessary for the production of heat by this tissue. “Developing molecules that activate this pathway is an avenue for burning fat and enabling weight loss, a prospect of interest in the fight against obesity and its complications,” indicated Etienne Mouisellecturer at the University of Toulouse III – Paul Sabatier and main author of the research.