IRS1 and Insulin resistance: The hypertrophic adipocytes secrete pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), interleukin 8 (IL-8), and monocyte chemoattractant protein 1 (MCP-1) which, through the phosphorylation of insulin receptor substrate-1 (IRS-1), cause insulin resistance.