Insulin Resistance in Type 2 Diabetes

Impaired insulin sensitivity, also termed insulin resistance, is generally defined as reduced glucose clearance in skeletal muscle, impaired suppression of glucose production by the liver, and decreased rates of lipolysis in adipose tissue or by decreased combined action on whole-body glucose disposal. Insulin resistance may occur independently of inadequate insulin secretion and be a prerequisite for incident type 2 diabetes. The liver plays a key role in the transition from the fasted to the fed state by its unique ability to switch rapidly from a glucose-producing organ to a glucose-storing organ. Adipose tissue is highly sensitive to the action of insulin on lipolysis in healthy humans, but not in states of insulin resistance and type 2 diabetes, which are also characterized by elevations in plasma concentrations of triglycerides and fatty acids.