With obesity, fat cells behave like infected

Inflammation of adipose tissue is a component of a vicious circle of events leading to the development of type 2 diabetes in some obese people. However, until now, experts did not understand what triggers these inflammatory reactions and for what reason.

Scientists at The Methodist Hospital, working under the leadership of Willa Hsueh, claim that at least part of the problem is the adipocyte fat cells themselves. In experiments on the cells of obese people and mice kept on a high-calorie diet, they found that excessive intake of nutrients from the bloodstream, transformed into fats and deposited in adipocytes, enhances the synthesis of the hormone leptin, an excess of which stimulates the production of gamma interferon by immune cells CD4⁺ T-lymphocytes. This signaling compound, in turn, triggers the synthesis of class II histocompatibility complex proteins in fat cells.

Usually these proteins are expressed by cells in order to attract the attention of the immune system to a pathogen (bacteria or virus) that has entered the body. It turns out that the cause of the development of the inflammatory status of adipose tissue is a false alarm signal sent by adipocytes to the immune system. In the future, this process is increasingly aggravated and other cells of the immune system – macrophages - are involved in it.

Specialists were previously aware of the active participation of T-lymphocytes and macrophages in the inflammation of adipose tissue, but until now no one could understand what acts as the trigger mechanism of this inflammatory reaction.

Finding out that the cause of the development of adipose tissue inflammation is the production by adipocytes of proteins of the main histocompatibility complex of class II indicates a fundamentally new target for drug therapy of obesity. Blocking this reaction of adipocytes to the intake of excess nutrients in itself will not cure obesity, but it will help to alleviate the most unfavorable manifestations of this condition during the course of complex therapy.

Article by Tuo Deng et al. Class II Major Histocompatibility Complex Plays an Essential Role in Obesity-Induced Adipose Inflammation published in the journal Cell Metabolism.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of The Methodist Hospital System:
Obesity makes fat cells act like they're infected.

07.03.2013