CCL2 and obesity due to melanocortin 4 receptor deficiency: Analogously, MCP-1 is associated with insulin resistance, hepatic steatosis, and macrophage infiltration in adipose tissue [55]; indeed, the addition of MCP-1 to differentiated 3T3-L1-derived adipocytes decreases insulin-induced glucose uptake and the expression of specific genes such as PPARγ and GLUT-4, contributing to a pathological condition related to hyperinsulinemia and obesity [56].