Interleukin-6 as a “metabolic hormone”

•Beyond its immunological roles, Interleukin-6 has been shown to play important metabolic roles.•Such metabolic implications covers lipids, glucose, proteins as well as energy balance.•The applications of this metabolic implications include therapy, research and diagnosis.•The highlighted physiological functions of IL-6 point IL-6 as a “metabolic hormone”. Interleukin 6 (IL-6) is a cytokine that is involved in divers immune responses and implicated in a number of diseases. However, this cytokine has other non-immune functions. Within this review, we highlight selected effects on metabolic pathways, which are mediated, controlled or modified by the IL-6. Importantly, putting spotlight on such concepts could allow us to classify IL-6 among the metabolic hormones and further study it to both deepen our knowledge on disorders involving metabolic or energy imbalances such as obesity and develop novel therapeutic strategies. Furthermore, potential explanations related to IL-6 roles in both physiology and pathology as well as relevant implications and applications on both research and therapeutic fields are also pointed as consequences of the involvement of IL-6 in the energy and metabolic homeostasis via its “endocrine” roles.