Fig. 1.

Adipose tissue, liver and skeletal muscle cross talk in obesity and insulin resistance. The liver maintains normoglycemia during fasting via glycogenolysis and gluconeogenesis. Following a meal, increased glucose delivery to the pancreas stimulates insulin secretion, which acts on the liver, adipose tissue and skeletal muscle. The primary action of insulin on the liver is to suppress hepatic glucose output, while insulin increases glucose uptake by the skeletal muscle and adipose tissue. Insulin additionally inhibits lipolysis in adipose tissue. In obesity, changes in adipokines produced and released from adipose tissue, such as decreased adiponectin and increased TNF-α and other inflammatory cytokines, coupled with increased free fatty acids contribute to hepatic and skeletal muscle insulin resistance.