Fig. 1.

Adipocytes are the main cell population in AT. However, several types of cells are commonly found in AT which their number varies in lean and obese AT, for example, while the number of M1 macrophages, MCs, and neutrophils increases in obesity, the number of AT resident Th2, Treg, and eosinophils decreases. AT in obesity is infiltrated by inflammatory cells, and the formation of crown-like structures characterized by circled necrotic/damaged adipocytes with macrophages is a common finding. Adipocytes not only store lipids but also release several cytokines and adipokines that influence immune responses and hemostasis of the tissue. An increase in number and the size of adipocytes surrounding the vasculature system results in the formation of physical pressure and consequent disruption of blood flow. MCs through inducing the release of cysteinyl cathepsins from endothelial and adipocytes play a role in catabolizing fibronectin