TNF and Insulin resistance: With the induction of lipopolysaccharide and saturated fatty acid, M1 macrophages can activate and secrete tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), interleukin-12 (IL-12), interleukin-1β (IL-1β) and other pro-inflammatory factors, leading to inflammation and insulin resistance (Table 1) (21).