IL-6 and TNF-α, which can be elevated in obesity and insulin resistance, have been confirmed to inhibit endothelial-dependent vasodilatation (40), and the degenerative endothelial vasodilatation in response to IL-6 and TNF-α can result in the reduction of NO availability (41). Here, IL6 is linked to obesity due to melanocortin 4 receptor deficiency.