Metabolism Tailors Macrophage Functions: One Size Does Not Fit All

It is well established that macrophages are critical for maintaining tissue integrity. It follows that impaired or exacerbated macrophage functions are often associated to disease. This is true in inflammatory related disorders, such as obesity, in which tissue macrophages become dysfunctional and display a persistent inflammatory activity. Conversely, in cancer, macrophages acquire an anti-inflammatory, immunosuppressive and pro-angiogenic function, sustaining, rather than constraining, tumor development and metastasis formation [1,2]. In all these pathological conditions macrophages receive signals from the surrounding tissues, engaging in a very complex plethora of functional states that support disease. Emerging research is now showing that in vitro polarized macrophages display different metabolic features, which are associated to their effector functions [3,4]. Yet, it is not completely clear if this holds true in vivo, and if specific metabolic traits impose a defined phenotype or vice versa, since the in vivo complexity of macrophage heterogeneity together with the impact that environmental signals can have on their phenotypic skewing would require a temporal and spatial definition that is strongly awaited. The present collection aims at providing an effective tool to contribute to the comprehensive understanding of the immunometabolic functions of macrophages and their communication with tissues in vivo in the context of two specific diseases: obesity and cancer.