Adiponectin resistance and vascular dysfunction in the hyperlipidemic state

Insulin plays an important role in the stimulation of vascular nitric oxide production, with both short term (vasomotility and anti-thrombotic effects) and long term (smooth muscle cell growth and migration inhibition) benefits. Impaired vasodilatory response to insulin, the hallmark of vascular insulin resistance (IR), has important implications for circulatory pathophysiology. An association between adipokines and IR has been observed in both diabetic and nondiabetic states. Adiponectin (APN) is an insulin-sensitizing adipokine known to stimulate skeletal muscle fatty acid (FA) oxidation and reduce lipid accumulation. Recent demonstrations of potential cross-talk between APN and insulin in vascular function regulation are particularly interesting. The lipid accumulation observed after chronic high-fat (HF) diets and in the obese state may reduce vascular response to APN, a pathologic state termed as APN resistance. This review highlights the importance of insulin sensitivity and APN activity in the maintenance of endothelial function. It explores the relationships between vascular IR and APN resistance in the hyperlipidemic pathological condition, representative of the metabolic syndrome. The investigation of vascular insulin and APN resistance provides not only better understanding of vascular pathophysiology, but also an opportunity for therapeutic targeting in individuals affected by the metabolic syndrome.