TNF and metabolic disease: Under the influence of pathological states, such as obesity, diabetes and hypertension, which are metabolic diseases, PVAT becomes dysfunctional and secretes high levels of pro-inflammatory factors such as leptin, resistin, inflammatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin (IL) -6, and chemokines such as monocyte chemotactic protein-1 (MCP-1), which induce endothelial dysfunction, immune cell infiltration and inflammation, and ultimately promote the development of atherosclerosis (23, 24).