CCL2 and obesity due to melanocortin 4 receptor deficiency: In the current study, the results showed that the visceral adipose tissue expression levels of TNF-α and MCP-1 in normal group were significantly lower than those in obesity and T2DM groups (P < 0.01), which were consistent with the previous study where TNF-α and MCP-1 were elevated in poor glycemic control and good glycemic control overweight and obese patients [16], suggesting that the immune response of visceral adipose tissue was changed during the occurrence of obesity and T2DM.