Adipokines: A new view of adipose tissue

Abstract

Leptin is a hormone secreted by adipocytes whose effect on the sympathetic nervous system and endocrine function confers active participation in the control of energy expenditure and appetite. Its identification added to the fat tissues in the human body the role of a multifunctional organ that produces and secretes a number of bioactive peptides and proteins, called adipocytokines. Changes in the amount of fat tissue, such as the ones that occur in obesity, affect the production of most of these factors secreted by adipocytes. Even if these changes are frequently associated with many metabolic disorders and increased risk for cardiovascular diseases, the role of fat tissue in the development of these complications, considered its endocrine function, continue to be investigated. The concentration of various adipocytokines increase in obesity and have been associated with hypertension (angiotensinogen), fibrinolysis impairment (plasminogen activator inhibitor-1) and insulin resistance (protein that stimulates acylation, tumor necrosis factor-alpha, interleukine-6 and resistin). On the other hand, leptin and adiponectin affect insulin sensitivity. In obesity, insulin resistance is also associated with leptin resistance and reduced plasma levels of adiponectin. Leptin and adiponectin still have complementary and distinct organic functions: adiponectin has potent antiatherogenic activity while leptin participates in the control of food intake. Some medications used to control diabetes increase adiponectin production in rodents and humans, suggesting that the development of new medications that target the adipocytokines can represent a new therapeutic alternative to prevent insulin resistance and atherosclerosis in obese individuals.