Additionally, obesity is linked to abnormal islet function, insulin resistance, and overexpression of monocyte chemotactic protein 1 (MCP-1) (Kahn and Flier, 2000; Parimisetty et al., 2016), which may affect energy homeostasis and cause excessive fat to accumulate in the liver, kidneys, heart, and other vital organs of the body, resulting in metabolic syndrome and increased organ load (Krzysztoszek et al., 2015). Here, CCL2 is linked to obesity due to melanocortin 4 receptor deficiency.