Fig 5: Lean and obese adipose tissue immune function. In obesity macrophages are polarized towards M1 phenotype with pro-inflammatory properties, while M2 macrophages with immunoregulatory properties are predominant in lean AT. In obese AT, NFk-B signaling pathway will be activated upon overexpression of Toll-like receptor 4 (TLR-4). Upon activation of NFk-B signaling, monocyte chemoattractant protein-1 (MCP-1) and pro-inflammatory markers such as interleukins β, 6, 12 (IL1β IL-6, IL-12) and tumor necrosis factor-α (TNF-α) will be expressed.