Obesity, hypertension, and insulin resistance are characterized by microvascular dysfunction [53,69,97,119]. Dysfunction of the microvasculature at the level of both resistance vessels and the nutritive

capillary beds develops progressively along with an increase in adiposity, even in children [20,22,60]. Impaired microvascular endothelium-dependent RG-7388 clinical trial vasodilatation occurs in response to various vasodilators, including insulin [22,59,107]. Obese individuals demonstrate diminished capillary density [22], which is inversely associated with visceral adiposity as measured with MRI, and truncal subcutaneous adipose tissue using skinfold measurements [20]. In hypertension, the mechanisms regulating vasomotor tone are abnormal, leading to enhanced vasoconstriction or reduced vasodilator responses to various vasodilators, including

insulin [66,69,98]. Moreover, there are anatomic alterations in the structure of individual precapillary resistance vessels, such as an increase in their wall-to-lumen ratio. Finally, there are changes at the level of the microvascular network involving a reduction in the number of arterioles or capillaries within vascular beds of various tissues (e.g., muscle and skin), so called GSK1120212 in vivo vascular rarefaction [66,69,99]. Similar defects in microvascular function and structure are associated with insulin resistance, defined as decreased sensitivity and/or responsiveness to metabolic actions of insulin that promote glucose disposal. Capillary rarefaction is associated with insulin

resistance [74]. In non-diabetic obese Carnitine palmitoyltransferase II subjects, as well as non-diabetic, overweight, hypertensive patients, endothelium-dependent vasodilatation and capillary recruitment to reactive hyperemia are inversely associated with insulin sensitivity [22,99,107]. Even in healthy, normotensive, non-obese subjects, a direct relationship between insulin sensitivity and microvascular function can be discerned [100]. Taken together, microvascular dysfunction at the level of both resistance vessels and the nutritive capillary beds has been established in obesity, hypertension, and insulin resistance. Importantly, microvascular abnormalities that lead to impaired tissue perfusion in obesity, hypertension, and insulin resistance appear to represent a generalized condition that affects multiple tissues and organs. Not only peripheral microvascular function in skin and muscle but also coronary, retinal, and renal microvascular function is affected [69,94,120]. Consequently, impaired tissue perfusion seems involved in target-organ damage and complications that involve several vascular beds (e.g., retinopathy, lacunar stroke, microalbuminuria, and heart failure) [69]. Microvascular dysfunction has been shown to be a predictor of prognosis and of an increased incidence of cardiovascular events [69,94].