SPHK1 and obesity due to melanocortin 4 receptor deficiency: SphK1 affects the migration and activation of inflammatory cells like macrophages and lymphocytes, as well as the production of cytokines including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and IL-10, thus serving both pro-inflammatory and anti-inflammatory functions in obesity (28).