Macrophage dysfunction and insulin resistance
Petri T Kovanen
Obesity and associated insulin resistance are associated with increased numbers of infiltrating macrophages at various sites of white adipose tissue. The adipose tissue macrophages are considered to be a major cause of obesity-associated chronic low-grade inflammation. The macrophages present in adipose tissue secrete a wide variety of proinflammatory molecules including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), and plasminogen activator inhibitor-1 (PAI-1). These inflammatory molecules may have both local effects on neighboring adipocytes and systemic effects on cells in other tissues. The combination of such paracrine and endocrine actions of the macrophage-derived molecules contributes to insulin resistance in white adipose tissue, muscle and liver observed in obese patients with type 2 diabetes and metabolic syndrome.