Increased oxidative stress and various pro-inflammatory cytokines and chemokines, including tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), which might interfere with anti-inflammatory effects on insulin action, were associated with insulin resistance, obesity, and type 2 diabetes (23, 24). Here, IL6 is linked to obesity due to melanocortin 4 receptor deficiency.