Abstract
In this chapter, we will present M1-type macrophages as the key cells in the initiation of the acute inflammatory response, while M2-type macrophages are resolving inflammation and coordinate tissue repair. Tissue inflammation is not only caused by bacterial infection or tissue injury but also derives from changes in the concentration of nutrients and metabolites. We will provide examples of metabolic stress, such as disturbance of reverse cholesterol transport and ER stress. In contrast to infectious or traumatic stress, metabolic stress is often caused by lipid overload in the blood and in adipose tissue. Thus, the immune system is implicated in the regulation of metabolic homeostasis, while perturbations in this immune-metabolic network are often the basis of the different features of the metabolic syndrome.