Adiponectin: linking the metabolic syndrome to its cardiovascular consequences

Obesity and its related disorders, glucose intolerance, hypertension and hyperlipidemia, collectively named the metabolic syndrome, result in substantial cardiovascular morbidity and mortality. Recent data point to several underlying regulatory mechanisms through which obesity links these various outcomes. Adipose tissue is now understood to function not merely as a passive energy storage depot but as an active endocrine organ, producing a variety of bioactive substances termed adipocytokines. Adiponectin, an adipocytokine first described as the most abundant protein produced by adipocytes, appears to serve as a central regulatory protein in many of the physiologic pathways controlling lipid and carbohydrate metabolism, and to mediate various vascular processes. Adiponectin displays both anti-inflammatory and antiatherogenic properties. Unlike other adipocytokines, its levels are paradoxically decreased in obesity and insulin-resistance states including metabolic syndrome and diabetes, as well as hypertension and coronary artery disease. This review will detail the relationship of adiponectin to various features of obesity and insulin-resistance syndromes, as well as its relationship to the cardiovascular complications of these disorders.