FGF21 and obesity due to melanocortin 4 receptor deficiency: Adipose tissue, serving as a molecular network linking obesity, adipokine secretion, chronic inflammation, insulin resistance, and ERS, can secrete a variety of adipokines, including interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), leptin, adiponectin, Fibroblast Growth Factor 21 (FGF21), and vascular endothelial growth factor(VEGF), among others.