The role of adiponectin in endothelial dysfunction and hypertension.

It has been two decades since the discovery of adiponectin, and today its role in insulin resistance, inflammation, and atherosclerosis are areas of major interest. Production of adiponectin is reduced in all inflammatory processes and states of insulin resistance such as obesity, type 2 diabetes mellitus, and coronary artery disease. Adiponectin regulates carbohydrate metabolism, and may also regulate vascular homeostasis by affecting important signaling pathways in endothelial cells and modulating inflammatory responses in the subendothelial space. Clinical studies have demonstrated a relationship between serum adiponectin concentrations and the activity of the renin-angiotensin-aldosterone system (RAAS), causing changes in blood pressure. Antihypertensive therapy with angiotensin II receptor blockers (ARBs) has been demonstrated to increase adiponectin levels in 3-6 months. Adiponectin has also been shown to play a role in cardiac injury in modulation of pro-survival reactions, cardiac energy metabolism, and inhibition of hypertrophic remodeling. The effects of adiponectin on the cardiovascular system are believed to be partially mediated by the activation of 5' adenosine monophosphate-activated protein kinase (AMPK) and cyclooxygenase-2 (COX-2) pathways, reducing endothelial cell apoptosis, promoting nitric oxide production, decreasing tumor necrosis factor-alpha (TNF-α) activity, and preventing atherosclerotic proliferation and smooth muscle cell migration. Further evaluation of biologically active forms of adiponectin and its receptor should help to clarify how obesity affects the cardiovascular system.