Macrophages and inflammation

Abstract

Adipose tissue has been under focus in the last decades, and pivotal concepts have emerged from the studies of its complex biology. White adipose tissue is composed of mature adipocytes, precursors (preadipocytes), endothelial cells, macrophages, and other immune cells. The phenotype, amount, and biology of each adipose tissue component are profoundly altered in human obesity. Low-grade inflammation both at the local and systemic levels characterizes obesity and appears to have a key role in mediating the consequence of increased adipose tissue mass on metabolic and vascular comorbidities. Among the different cell types contributing to inflammation, this chapter focuses on the mechanisms and consequences of macrophage accumulation in obese adipose tissue. While differences probably exist between rodent models and human cases, macrophage cells have a very complex phenotype able to change with weight modification. It is not fully established whether macrophages exert a rather beneficial or deleterious role in the adipose tissue. In any case, the presence of these cells modifies the biology of adipose specialized cells such as preadipocytes and adipocytes. This chapter reviews the current knowledge regarding the contribution of monocytes/macrophages in development and maintenance of obesity and related complications both in mouse and human situations.