We have demonstrated that there is a cuff of adipose tissue around the origin of nutrient arterioles, isolated from cremaster muscles from obese Zucker rats [83,125]. Using a variety of insulin signaling pathway inhibitors, we have shown that in these animals, the PI3K insulin signaling pathway is impaired, and NO production is suppressed [83]. This has led us to propose that

in states of obesity, perivascular fat may signal to the vessel wall, both BMN 673 concentration locally (paracrine) and downstream (vasocrine), through outside-to-inside signaling [125]. Perivascular fat around nutrient arterioles may inhibit the effects of systemic insulin on local vasodilatation, with consequent inhibition of nutritive blood flow and insulin action. Recently, some evidence has been published in support of the hypothesis that obesity-related changes

in adipose tissue have direct effects on the vasoactive properties of perivascular adipose tissue [35]. Small arteries with and without perivascular adipose tissue were taken from subcutaneous gluteal fat biopsy samples and studied with wire myography and immunohistochemistry. It was demonstrated that healthy adipose tissue around human small arteries secretes adiponectin that influences vasodilatation by increasing NO bioavailability. Selleck Trametinib However, in perivascular fat from obese subjects with metabolic syndrome, the loss of this dilator effect was accompanied by an increase in adipocyte area and immunohistochemical evidence of inflammation, with increased activity of TNF-α. In isolated resistance arteries of the rat

cremaster muscle, we could demonstrate that adiponectin influences insulin signaling in the endothelium by activating AMPK in microvascular endothelium, and inhibiting insulin’s vasoconstrictor effects, leading to overall insulin-mediated vasodilatation [28]. In concordance with these findings, other preliminary data in mice suggest PAK5 that PVAT controls insulin-mediated vasodilatation in muscle arterioles by secreting adiponectin (abstract, 9th World Congress for Microcirculation, 2010). This mechanism is impaired in db/db mice, leading to impaired insulin-mediated vasodilatation. The possible origins and driving forces behind the deposition of PVAT are currently under investigation. In conclusion, elevated FFA and TNF-α concentrations and decreased adiponectin concentrations are likely candidates to link (perivascular) adipose tissue with defects in microvascular function, at least in part, by influencing insulin signaling and thereby insulin’s vascular effects. Obesity has been implicated in the rising prevalence of the metabolic syndrome, a cluster of risk factors including, hypertension, insulin resistance, which confer an increased risk for type 2 diabetes and CVD.