Adipose tissue and adipokines: for better or worse

It is now recognized that the white adipose tissue (WAT) produces a variety of bioactive peptides, collectively termed "adipokines". Alteration of WAT mass in obesity or lipoatrophy, affects the production of most adipose secreted factors. Since both conditions are associated with multiple metabolic disorders and increased risk of cardiovascular diseases, the idea has emerged that WAT could be instrumental in these complications, by virtue of its secreted factors. Several adipokines are increased in the obese state and have been implicated in hypertension (angiotensinogen), impaired fibrinolysis (PAI-1) and insulin resistance (ASP, TNFalpha, IL-6, resistin). Conversely, leptin and adiponectin both exert an insulin-sensitizing effect, at least in part, by favoring tissue fatty-acid oxidation through activation of AMP-activated kinase. in obesity, insulin resistance has been linked to leptin resistance and decreased plasma adiponectin. In lipoatrophic mice, where leptin and adiponectin circulating levels are low, administration of the two adipokines synergistically reverses insulin resistance. Leptin and adiponectin also have distinct properties: leptin, as a long-term integrative signal of energy store and adiponectin, as a potent antiatherogenic agent. The thiazolidinedione anti-diabetic drugs increase endogenous adiponectin production in rodents and humans, supporting the idea that the development of new drugs targeting adipokines might represent a promising therapeutic approach to protect obese patients from insulin resistance and atherosclerosis.