CCL2 and obesity due to melanocortin 4 receptor deficiency: Proinflammatory mediators (cytokines and chemokines), such as tumor necrosis factor (TNF)α; interleukin (IL)-6; monocyte chemoattractant protein (MCP)-1; regulated on activation, normal T cell expressed and secreted (RANTES); and macrophage inflammatory protein (MIP)-1α (amongst others), can adversely impact skeletal muscle function in obesity and/or recruit immune cells in obese and insulin-resistant skeletal muscle and promote pro-inflammatory cross-talk between immune and skeletal muscle cells [37,38,39].