Objectives: 

Interleukin-6(IL-6)has been involved in the control of body weight and body fat. Nevertheless, the mechanisms underlying these effects are not completely understood because central and peripheral actions of IL-6 are plausible. To gain further insight into the effects of IL-6 on energy homeostasis we used different animal models: mice that express the I-6 gene under the control of the GFAP promoter, Il-6 Knockout mice, as well as mice with IL-6 gene selectively deleted in adipose tissue or skeletal muscle, main tissues producing IL-6 in physiological situations.

Materials: 

In these animals we have controlled body weight, food intake, different biochemical and hormonal parameters and the expression of the main hypothalamic neuropeptides involved in the control of food intake and energy expenditure (NPY, AgRP, TRH, preproOx, POMC and CRH). We used animals of both sexes, different ages and different feeding conditions (fasting, high and low fat diet).

Results: 

Our results indicate that IL-6 has a role in the energy homeostasis acting mainly at the central level by regulating the expression of NPY, AgRP, POMC and, CRH, although peripheral effects of IL-6 can not be discarded. The effect of IL-6 is dependent on sex and age and on the tissue where IL-6 is synthesized, reflecting the complicated regulatory functions of this protein.

Conclusions: 

IL-6 has been considered and inflammatory cytokine important in immune response but in the absence of inflammation is synthesized in muscle and adipose tissue playing a role in body weight regulation, fat mass and metabolic functions.