CCL2 and obesity due to melanocortin 4 receptor deficiency: To further investigate whether chlorpyrifos could cause low-grade inflammation through the LPS pathway, expression of the major pro-inflammatory mediators involved in IR and obesity in the liver (TNF-α) and adipose tissue (TNF-α, MCP-1, IL-1 β, PAI-1) was examined (Fig. 3f, n).